drm/amd/display: enable clock gating and dchubp power gating

also refactor to clean reduce loc to achieve same logic

Signed-off-by: Tony Cheng <tony.cheng@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Reviewed-by: Yongqiang Sun <yongqiang.sun@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>