Revert "drm/amd/display: New path for enabling DPG"

This reverts commit f8e792dc



[Why]
We are not implementing the planned new HW
sequence for HUBP disable.

[How]
Revert most related changes to minimize regressions.

Signed-off-by: Wesley Chalmers <Wesley.Chalmers@amd.com>
Reviewed-by: Martin Leung <Martin.Leung@amd.com>
Acked-by: Qingqing Zhuo <Qingqing.Zhuo@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>