drm/amd/display: Improve HDMI info retrieval

drm/amd/display: Improve HDMI info retrieval

[WHY & HOW]
Make a dedicated function to read HDMI-related monitor info, including
monitor's SCDC support.

Fixes: 3471b9a31ce3 ("drm/amd/display: Rework HDMI data channel reads")
Suggested-by: Fangzhi Zuo <jerry.zuo@amd.com>
Reviewed-by: Jerry Zuo <jerry.zuo@amd.com>
Signed-off-by: Ivan Lipski <ivan.lipski@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit c78e31bcf586f1c910a2636650840f5ce1cb1c63)