After configuration, the host also possible sends bus reset
at any time, at such situation, it will trigger below spinlock
recursion dump. This commit unlocks the spinlock before calling
gadget's disconnect.

BUG: spinlock recursion on CPU#0, swapper/0/0
 lock: 0xbf128014, .magic: dead4ead, .owner: swapper/0/0, .owner_cpu: 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.11.0-next-20130910+ #106
[<80014e20>] (unwind_backtrace+0x0/0xec) from [<80011a6c>] (show_stack+0x10/0x14)
[<80011a6c>] (show_stack+0x10/0x14) from [<805c143c>] (dump_stack+0x94/0xbc)
[<805c143c>] (dump_stack+0x94/0xbc) from [<80282cf8>] (do_raw_spin_lock+0x16c/0x18c)
[<80282cf8>] (do_raw_spin_lock+0x16c/0x18c) from [<805c77e0>] (_raw_spin_lock_irqsave+0x50/0x5c)
[<805c77e0>] (_raw_spin_lock_irqsave+0x50/0x5c) from [<803cff88>] (ep_disable+0x24/0x110)
[<803cff88>] (ep_disable+0x24/0x110) from [<7f015d50>] (gserial_disconnect+0xa0/0x15c [u_serial])
[<7f015d50>] (gserial_disconnect+0xa0/0x15c [u_serial]) from [<7f01c06c>] (acm_disable+0xc/0x30 [usb_f_acm])
[<7f01c06c>] (acm_disable+0xc/0x30 [usb_f_acm]) from [<7f001478>] (reset_config.isra.10+0x34/0x5c [libcomposite])
[<7f001478>] (reset_config.isra.10+0x34/0x5c [libcomposite]) from [<7f0014d4>] (composite_disconnect+0x34/0x5c [libcomposite])
[<7f0014d4>] (composite_disconnect+0x34/0x5c [libcomposite]) from [<803d1024>] (udc_irq+0x770/0xce4)
[<803d1024>] (udc_irq+0x770/0xce4) from [<803cdcc0>] (ci_irq+0x98/0x164)
[<803cdcc0>] (ci_irq+0x98/0x164) from [<8007edfc>] (handle_irq_event_percpu+0x50/0x17c)
[<8007edfc>] (handle_irq_event_percpu+0x50/0x17c) from [<8007ef64>] (handle_irq_event+0x3c/0x5c)
[<8007ef64>] (handle_irq_event+0x3c/0x5c) from [<80081e98>] (handle_fasteoi_irq+0x98/0x168)
[<80081e98>] (handle_fasteoi_irq+0x98/0x168) from [<8007e598>] (generic_handle_irq+0x28/0x3c)
[<8007e598>] (generic_handle_irq+0x28/0x3c) from [<8000edf4>] (handle_IRQ+0x4c/0xb4)
[<8000edf4>] (handle_IRQ+0x4c/0xb4) from [<800085bc>] (gic_handle_irq+0x28/0x5c)
[<800085bc>] (gic_handle_irq+0x28/0x5c) from [<800125c0>] (__irq_svc+0x40/0x54)
Exception stack(0x8083bf68 to 0x8083bfb0)
bf60:                   81533b80 00000000 00096234 8001d760 8088e12c 00000000
bf80: 8083a000 8083a000 8084290c 805cb414 808428ac 8083a000 00000001 8083bfb0
bfa0: 8000f138 8000f13c 60000013 ffffffff
[<800125c0>] (__irq_svc+0x40/0x54) from [<8000f13c>] (arch_cpu_idle+0x30/0x3c)
[<8000f13c>] (arch_cpu_idle+0x30/0x3c) from [<8005eb94>] (cpu_startup_entry+0xf4/0x148)
[<8005eb94>] (cpu_startup_entry+0xf4/0x148) from [<807f1a2c>] (start_kernel+0x2c4/0x318)
BUG: spinlock lockup suspected on CPU#0, swapper/0/0
 lock: 0xbf128014, .magic: dead4ead, .owner: swapper/0/0, .owner_cpu: 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.11.0-next-20130910+ #106
[<80014e20>] (unwind_backtrace+0x0/0xec) from [<80011a6c>] (show_stack+0x10/0x14)
[<80011a6c>] (show_stack+0x10/0x14) from [<805c143c>] (dump_stack+0x94/0xbc)
[<805c143c>] (dump_stack+0x94/0xbc) from [<80282c94>] (do_raw_spin_lock+0x108/0x18c)
[<80282c94>] (do_raw_spin_lock+0x108/0x18c) from [<805c77e0>] (_raw_spin_lock_irqsave+0x50/0x5c)
[<805c77e0>] (_raw_spin_lock_irqsave+0x50/0x5c) from [<803cff88>] (ep_disable+0x24/0x110)
[<803cff88>] (ep_disable+0x24/0x110) from [<7f015d50>] (gserial_disconnect+0xa0/0x15c [u_serial])
[<7f015d50>] (gserial_disconnect+0xa0/0x15c [u_serial]) from [<7f01c06c>] (acm_disable+0xc/0x30 [usb_f_acm])
[<7f01c06c>] (acm_disable+0xc/0x30 [usb_f_acm]) from [<7f001478>] (reset_config.isra.10+0x34/0x5c [libcomposite])
[<7f001478>] (reset_config.isra.10+0x34/0x5c [libcomposite]) from [<7f0014d4>] (composite_disconnect+0x34/0x5c [libcomposite])
[<7f0014d4>] (composite_disconnect+0x34/0x5c [libcomposite]) from [<803d1024>] (udc_irq+0x770/0xce4)
[<803d1024>] (udc_irq+0x770/0xce4) from [<803cdcc0>] (ci_irq+0x98/0x164)
[<803cdcc0>] (ci_irq+0x98/0x164) from [<8007edfc>] (handle_irq_event_percpu+0x50/0x17c)
[<8007edfc>] (handle_irq_event_percpu+0x50/0x17c) from [<8007ef64>] (handle_irq_event+0x3c/0x5c)
[<8007ef64>] (handle_irq_event+0x3c/0x5c) from [<80081e98>] (handle_fasteoi_irq+0x98/0x168)
[<80081e98>] (handle_fasteoi_irq+0x98/0x168) from [<8007e598>] (generic_handle_irq+0x28/0x3c)
[<8007e598>] (generic_handle_irq+0x28/0x3c) from [<8000edf4>] (handle_IRQ+0x4c/0xb4)
[<8000edf4>] (handle_IRQ+0x4c/0xb4) from [<800085bc>] (gic_handle_irq+0x28/0x5c)
[<800085bc>] (gic_handle_irq+0x28/0x5c) from [<800125c0>] (__irq_svc+0x40/0x54)
Exception stack(0x8083bf68 to 0x8083bfb0)
bf60:                   81533b80 00000000 00096234 8001d760 8088e12c 00000000
bf80: 8083a000 8083a000 8084290c 805cb414 808428ac 8083a000 00000001 8083bfb0
bfa0: 8000f138 8000f13c 60000013 ffffffff
[<800125c0>] (__irq_svc+0x40/0x54) from [<8000f13c>] (arch_cpu_idle+0x30/0x3c)
[<8000f13c>] (arch_cpu_idle+0x30/0x3c) from [<8005eb94>] (cpu_startup_entry+0xf4/0x148)
[<8005eb94>] (cpu_startup_entry+0xf4/0x148) from [<807f1a2c>] (start_kernel+0x2c4/0x318)
Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>