drm/amd/display: Update dchub and dpp as per update flags.

Check update flags and update dchub and dpp as per flags,
reduce reg access from 347 to 200, duration time reduce
to 170us.

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