drm/i915/cnp: Panel Power sequence changes for CNP PCH.

drm/i915/cnp: Panel Power sequence changes for CNP PCH.

Panel Power sequences for CNP is similar to Broxton,
but with only one sequencer.

Main difference from SPT is that PP_DIVISOR was removed
and power cycle delay has been moved to PP_CONTROL.

v2: Add missed pp_div write, that is now part of PP_CONTROL[8:4]
    as on Broxton. (Found by DK)

v3: Improve commit message. (By DK)

Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Clinton Taylor <clinton.a.taylor@intel.com>
Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1496434004-29812-6-git-send-email-rodrigo.vivi@intel.com