pinctrl: apple: Always return valid type in apple_gpio_irq_type

pinctrl: apple: Always return valid type in apple_gpio_irq_type

apple_gpio_irq_type can possibly return -EINVAL which triggers the
following compile error with gcc 9 because the type no longer fits
into the mask.

  drivers/pinctrl/pinctrl-apple-gpio.c: In function 'apple_gpio_irq_set_type':
  ././include/linux/compiler_types.h:335:38: error: call to '__compiletime_assert_289' declared with attribute error: FIELD_PREP: value too large for the field
    335 |  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
        |                                      ^
  [...]
  drivers/pinctrl/pinctrl-apple-gpio.c:294:7: note: in expansion of macro 'FIELD_PREP'
    294 |       FIELD_PREP(REG_GPIOx_MODE, irqtype));
        |       ^~~~~~~~~~

Fix this by making the return value always valid and instead checking
for REG_GPIOx_IN_IRQ_OFF in apple_gpio_irq_set_type and return -EINVAL
from there.

Fixes: a0f160ffcb83 ("pinctrl: add pinctrl/GPIO driver for Apple SoCs")
Signed-off-by: Sven Peter <sven@svenpeter.dev>
Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Link: https://lore.kernel.org/r/20211101150640.46553-1-sven@svenpeter.dev
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>