Add new CGS interfaces to query display info across modules.
This is nedded by the powerplay module for synchronizing with
the display module.

v2: (agd): fold in refresh rate fix, rebase
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Reviewed-by: Jammy Zhou <Jammy.Zhou@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>