gpio: add missing MODULE_DESCRIPTION() macros

gpio: add missing MODULE_DESCRIPTION() macros

On x86, make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/gpio/gpio-gw-pld.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/gpio/gpio-mc33880.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/gpio/gpio-pcf857x.o

Add the missing invocations of the MODULE_DESCRIPTION() macro,
including the one missing in gpio-pl061.c, which is not built for x86.

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Link: https://lore.kernel.org/r/20240606-md-drivers-gpio-v1-1-cb42d240ca5c@quicinc.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>