drm/amd/powerplay: determine the features to enable by pptable only

Per current logics, the features to enable are determined together
by driver and pptable. This is not efficient in co-debug with
firmware team.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Kenneth Feng <kenneth.feng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>