Similar to omap_gpio_irq_type() let's make sure that the GPIO
is usable as an interrupt if the platform init code did not
call gpio_request(). Otherwise we can get invalid device access
after setup_irq():

WARNING: CPU: 0 PID: 1 at drivers/bus/omap_l3_noc.c:147 l3_interrupt_handler+0x214/0x340()
44000000.ocp:L3 Custom Error: MASTER MPU TARGET L4CFG (Idle): Data Access in Supervisor mode during Functional access
...
[<c05f21e4>] (__irq_svc) from [<c05f1974>] (_raw_spin_unlock_irqrestore+0x34/0x44)
[<c05f1974>] (_raw_spin_unlock_irqrestore) from [<c00914a8>] (__setup_irq+0x244/0x530)
[<c00914a8>] (__setup_irq) from [<c00917d4>] (setup_irq+0x40/0x8c)
[<c00917d4>] (setup_irq) from [<c0039c8c>] (omap_system_dma_probe+0x1d4/0x2b4)
[<c0039c8c>] (omap_system_dma_probe) from [<c03b2200>] (platform_drv_probe+0x44/0xa4)
...

We can fix this the same way omap_gpio_irq_type() is handling it.

Note that the long term solution is to change the gpio-omap driver
to handle the banks as separate driver instances. This will allow
us to rely on just runtime PM for tracking the bank specific state.
Reported-by: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Javier Martinez Canillas <javier@dowhile0.org>
Cc: Kevin Hilman <khilman@kernel.org>
Cc: Santosh Shilimkar <ssantosh@kernel.org>
Tested-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>