drm/i915: Fix chv cdclk support

The specs seem to be full of misinformation wrt. the Punit register
0x36. Some versions still show the old VLV bit layout, some the new
layout, and all of them seem to tell us nonsense about the cdclk
value encoding.

Testing on actual hardware has shown that we simply need to program
the desired CCK divider into the Punit register using the new layout of
the bits. Doing that, the status bit change to indicate the same value,
and the CCK 0x6b register also changes accordingly to indicate that CCK
is now using the new divider.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Vijay Purushothaman <vijay.a.purushothaman@linux.intel.com>
Reviewed-by: Yogesh Mohan Marimuthu <yogesh.mohan.marimuthu@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>