gpio: uniphier: Bail out on gpiochip_lock_as_irq() error

gpiochip_lock_as_irq() may return a few error codes,
bail out if it fails with corresponding returned code.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>