gpiolib: Check gc->get_direction() before calling gpiod_get_direction()

gpiolib: Check gc->get_direction() before calling gpiod_get_direction()

According to 'struct gpio_chip' documentation in linux/gpio/driver.h,
implementing .get_direction() is recommended but not mandatory.
Most places verify that gc->get_direction() exists before calling
gpiod_get_direction(), but gpiolib_dbg_show() doesn't.

Until commit 471e998c0e31 ("gpiolib: remove redundant callback check")
it was also verified by gpiod_get_direction() itself so calling it at
all time from gpiolib_dbg_show() was not an issue. But after the check
in gpiod_get_direction() has been removed, calling it inconditionaly
leads to a big fat warning in gpiochip_get_direction().

In gpiod_get_direction(), verify that gc->get_direction() exists
before calling gpiod_get_direction().

Fixes: 471e998c0e31 ("gpiolib: remove redundant callback check")
Signed-off-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Link: https://patch.msgid.link/ad89f92f91d004e63dd5599bb58e9581f373a601.1785318183.git.chleroy@kernel.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>