Allwinner: a10_gpio Fix panic on multiple lock

r323392 introduce gpio_pin_get/gpio_pin_set for a10_gpio driver.
When called via gpio method they must aquire the device lock while
when they are called via gpio_pin_configure the lock is already aquire.

Introduce a10_gpio_pin_{s,g}et_locked and call them in pin_gpio_configure
instead.

Tested On: BananaPi (A20)

Reported by: Richard Puga richard@puga.net