drm/amd/display: Add more Clock Sources to DCN2.1

[WHY]
When enabling HDMI on ComboPHY, there are not
enough clock sources to complete display detection.

[HOW]
Initialize more clock sources.

Signed-off-by: Sung Lee <sung.lee@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>