drm/amdgpu/atom: add support for new SetPixelClock table

New version of the SetPixelClock table for elm/baf.  The
new table calculates the pll dividers and handles spread
spectrum calculations and setup.

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>