drm/amd/display: Removing 2 phys

[WHY]
New dcn301 has 2 less phys

Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Pavle Kotarac <Pavle.Kotarac@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>