drm/amd/display: Handle Renoir in amdgpu_dm (v2)

Hook up renoir support to KMS.

v2: squash in "Fixes for Renoir in amdgpu_dm"

Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>