drm/i915/cnl: Implement CNL display init/unit sequence

Implement the CNL display init/uninit sequence as outlined in Bspec.

Quite similar to SKL/BXT. The main complicaiton is probably the extra
procmon setup we must do based on the process/voltage information we
can read out from some register.

v2: s/skl_dbuf/gen9_dbuf/ to follow upstream
    bxt needed a cdclk sanitize step, so let's add it for cnl too
v3: s/CHICKEN_MISC_1/CHICKEN_MISC_2/ (Ander)
v4: Rebased by Rodrigo after Ville's cdclk rework
v5: Removed unecessary Aux IO forced enable/disable, Fix DW10 setup
    Fix procpon Mask. (Credits-to Paulo and Clint)
    Remove A0 workaround.
v6: Rebased on top of recent code (Rodrigo).
v7: Respect the order of sanitize_ after set_
    (Done by Rodrigo, Requested by Ville)
v8: Commit message updated to matvh v5 changes besides
    Remove unused DW8 and an extra blank line. (all noticed
    by Imre).
v9: Remove __attribute__((unused)) added on latest version
    of drm/i915/cnl: Implement .set_cdclk() for CNL.

Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Clint Taylor <clinton.a.taylor@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1497047175-27250-3-git-send-email-rodrigo.vivi@intel.com