drm/i915: Pass the cdclk state to the set_cdclk() functions

Rather than passing all the different parameters (cdclk,vco so
far) sparately to the set_cdclk() functions, just pass the
entire cdclk state.

v2: Deal with churn
v3: Drop the usless .ref assignment (Ander)

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ander Conselvan de Oliveira <conselvan2@gmail.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170120182205.8141-11-ville.syrjala@linux.intel.com