drm/amd/display: dce110: fix plane validation

drm/amd/display: dce110: fix plane validation

For MPO to work with per surface rendering and flipping,
the previous logic of restricting plane[1] only as underlay
needs to be removed.
validate_surface_sets() now checks only the width and height
bounds in case of underlay rather than checking format.

Without this patch one cannot set underlay only.

Signed-off-by: Shirish S <shirish.s@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>