gpio: amd-fch: ionly return allowed values from amd_fch_gpio_get()

gpio: amd-fch: ionly return allowed values from amd_fch_gpio_get()

As of 86ef402d805d ("gpiolib: sanitize the return value of
gpio_chip::get()") gpiolib requires drivers implementing GPIOs to only
return 0, 1 or negative error for the get() callbacks. Ensure that
amd-fch complies with this requirement.

Fixes: 86ef402d805d ("gpiolib: sanitize the return value of gpio_chip::get()")
Reported-and-tested-by: Tj <tj.iam.tj@proton.me>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Link: https://patch.msgid.link/aZTlwnvHt2Gho4yN@google.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>