Normally, ADAP_STREAMING bit is set in dvb_usb_start_feed and cleared in
dvb_usb_stop_feed.

But in exceptional cases, for example, when the tv is playing programs
and the tuner is pulled out, then dvb_usbv2_disconnect is called.

In such case, it will first call dvb_usbv2_adapter_frontend_exit to stop
dvb_frontend_thread, and then call dvb_usbv2_adapter_dvb_exit to clear
ADAP_STREAMING bit.

At this point, if dvb_frontend_thread is sleeping and waiting for
ADAP_STREAMING to be cleared to get out of sleep. then
dvb_frontend_thread can never be stoped, because clearing ADAP_STREAMING
bit is performed after dvb_frontend_thread is stopped (i.e. performed in
dvb_usbv2_adapter_dvb_exit).

So, deadlock:

[  240.822037] INFO: task khubd:497 blocked for more than 120 seconds.
[  240.822655] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  240.830493] khubd           D c0013b3c     0   497      2 0x00000000
[  240.836996] [<c0013b3c>] (__schedule+0x200/0x54c) from [<c00110f4>] (schedule_timeout+0x14c/0x19c)
[  240.845940] [<c00110f4>] (schedule_timeout+0x14c/0x19c) from [<c00137f4>] (wait_for_common+0xac/0x150)
[  240.855234] [<c00137f4>] (wait_for_common+0xac/0x150) from [<c004989c>] (kthread_stop+0x58/0x90)
[  240.864004] [<c004989c>] (kthread_stop+0x58/0x90) from [<c03b2ebc>] (dvb_frontend_stop+0x3c/0x9c)
[  240.872849] [<c03b2ebc>] (dvb_frontend_stop+0x3c/0x9c) from [<c03b2f3c>] (dvb_unregister_frontend+0x20/0xd8)
[  240.882666] [<c03b2f3c>] (dvb_unregister_frontend+0x20/0xd8) from [<c03ed938>] (dvb_usbv2_exit+0x68/0xfc)
[  240.892204] [<c03ed938>] (dvb_usbv2_exit+0x68/0xfc) from [<c03eda18>] (dvb_usbv2_disconnect+0x4c/0x70)
[  240.901499] [<c03eda18>] (dvb_usbv2_disconnect+0x4c/0x70) from [<c031c050>] (usb_unbind_interface+0x58/0x188)
[  240.911395] [<c031c050>] (usb_unbind_interface+0x58/0x188) from [<c02c3e78>] (__device_release_driver+0x74/0xd0)
[  240.921544] [<c02c3e78>] (__device_release_driver+0x74/0xd0) from [<c02c3ef0>] (device_release_driver+0x1c/0x28)
[  240.931697] [<c02c3ef0>] (device_release_driver+0x1c/0x28) from [<c02c39b8>] (bus_remove_device+0xc4/0xe4)
[  240.941332] [<c02c39b8>] (bus_remove_device+0xc4/0xe4) from [<c02c1344>] (device_del+0xf4/0x178)
[  240.950106] [<c02c1344>] (device_del+0xf4/0x178) from [<c0319eb0>] (usb_disable_device+0xa0/0x1c8)
[  240.959040] [<c0319eb0>] (usb_disable_device+0xa0/0x1c8) from [<c03128b4>] (usb_disconnect+0x88/0x188)
[  240.968326] [<c03128b4>] (usb_disconnect+0x88/0x188) from [<c0313edc>] (hub_thread+0x4d0/0x1200)
[  240.977100] [<c0313edc>] (hub_thread+0x4d0/0x1200) from [<c0049690>] (kthread+0xa4/0xb0)
[  240.985174] [<c0049690>] (kthread+0xa4/0xb0) from [<c0009118>] (ret_from_fork+0x14/0x3c)
[  240.993259] INFO: task kdvb-ad-0-fe-0:3256 blocked for more than 120 seconds.
[  241.000349] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  241.008162] kdvb-ad-0-fe-0  D c0013b3c     0  3256      2 0x00000000
[  241.014507] [<c0013b3c>] (__schedule+0x200/0x54c) from [<c03eda44>] (wait_schedule+0x8/0x10)
[  241.022924] [<c03eda44>] (wait_schedule+0x8/0x10) from [<c001120c>] (__wait_on_bit+0x74/0xb8)
[  241.031434] [<c001120c>] (__wait_on_bit+0x74/0xb8) from [<c00112b8>] (out_of_line_wait_on_bit+0x68/0x70)
[  241.040902] [<c00112b8>] (out_of_line_wait_on_bit+0x68/0x70) from [<c03e5e88>] (dvb_usb_fe_sleep+0xf4/0xfc)
[  241.050618] [<c03e5e88>] (dvb_usb_fe_sleep+0xf4/0xfc) from [<c03b4b74>] (dvb_frontend_thread+0x124/0x4e8)
[  241.060164] [<c03b4b74>] (dvb_frontend_thread+0x124/0x4e8) from [<c0049690>] (kthread+0xa4/0xb0)
[  241.068929] [<c0049690>] (kthread+0xa4/0xb0) from [<c0009118>] (ret_from_fork+0x14/0x3c)

Fix it by calling dvb_usbv2_adapter_frontend_exit() latter.

Test enviroment: odroidx2 + Hauppauge(WinTV-Aero-M)
Signed-off-by: Changbing Xiong <cb.xiong@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>