drm/amd/display: Add new GPINT command definitions

New commands for enabling copy of DC bounding box values from VBIOS DMUB

Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>