drm/amd/display: Clock does not lower in Updateplanes

[why]
We reset the optimized_required in atomic_plane_disable
flag immediately after it is set in atomic_plane_disconnect, causing us to
never have flag set during next flip in UpdatePlanes.

[how]
Optimize directly after each time plane is removed.

Signed-off-by: Murton Liu <murton.liu@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>