gpiolib: read descriptor flags once in gpiolib_dbg_show()

For consistency with most other code that can access requested
descriptors: read the flags once atomically and then test individual
bits from the helper variable. This avoids any potential discrepancies
should flags change during the debug print.

Link: https://lore.kernel.org/r/20250215100847.30136-1-brgl@bgdev.pl


Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>