drm/radeon: use new cg/pg flags for SI

Allows us finer grained control over clock and
powergating on SI.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --cc drivers/gpu/drm/radeon/radeon_asic.c
Simple merge

diff --cc drivers/gpu/drm/radeon/si.c
Simple merge