Input: gpio-keys - add support for setkeycode

gpio-keys input devices created by the soc_button_array driver are
configured with key-codes based on ACPI provided information.

Unfortunately on some tablets this info is wrong, and we need to have
a quirk to fix things up.

Add support for input_setkeycode to the gpio-keys driver, so that
the existing udev hwdb mechanism can be used to fix things up on these
tablets.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>