Limit CHV maximum cdclk to 320MHz.

v2: Rebase to the latest
v3: Clean up of if-else tree
Signed-off-by: NMika Kahola <mika.kahola@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>