gpio: fix GPIO submenu in Kconfig

gpio: fix GPIO submenu in Kconfig

Commit a86240a37d43 ("gpiolib: enable CONFIG_GPIOLIB_LEGACY even for
!GPIOLIB") accidentally pulled all items from within the GPIOLIB submenu
into the main driver menu. Put them back under the top-level GPIO entry.

Suggested-by: Rob Herring <robh@kernel.org>
Fixes: a86240a37d43 ("gpiolib: enable CONFIG_GPIOLIB_LEGACY even for !GPIOLIB")
Reported-by: Rob Herring <robh@kernel.org>
Closes: https://lore.kernel.org/all/20250813222649.GA965895-robh@kernel.org/
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20250901125513.108691-1-brgl@bgdev.pl
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>