drm/amdgpu/dce11: add dce clock setting for ELM/BAF

Setup the disp clock and dp reference clock.  This is
now a separate command table on elm/baf compared to
older asics.

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Jammy Zhou <Jammy.Zhou@amd.com>