drm/amd/display: Add DCN3.1 GPIO support

Extends off of DCN3.

Acked-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>