gpio: vf610: Allow building as a module

Support for building it as a module for use on the Android platform,
because the Android kernel(GKI) doesn't contain board-specific drivers,
it requires that these drivers be built as a module and loaded into the
system.

Signed-off-by: Jindong Yue <jindong.yue@nxp.com>
Link: https://lore.kernel.org/r/20250416062605.1948856-1-jindong.yue@nxp.com


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