HDMI 12bpc should be working fine now. Let it loose.

This reverts commit 5e3daaca.

v2: Rebased due to CHV/BXT port clock check improvemnts
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-and-tested-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>