We were returning with "chip->lock" held by mistake.  It's safe to
move the return to before we take the spinlock.

Fixes: 1dbf7f29 ('gpio: pl061: detail IRQ trigger handling')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>