When adding the gpiochip, the GPIO HW drivers' callback get_direction()
could get called in atomic context. Some of the GPIO HW drivers may
sleep when accessing the register.

Move the lock before initializing the descriptors.
Reported-by: NLaxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>