drm/i915/icl: Add icl pipe degamma and gamma support

Add support for icl pipe degamma and gamma.

v2: Removed a POSTING_READ and corrected the Bit
Definition as per Maarten's comments.

v3: Addressed Matt's review comments. Removed rmw patterns
as suggested by Matt.

v4: Fixed Matt's review comments.

v5: Corrected macro alignment as per Jani Nikula's comments.
Addressed Ville and Matt's  review comments.

v6: Merged ICL degamma handling with GLK and dropped ICL
degamma function as per Ville and Matt's comments.

v7: updated gamma_mode state with pre csc gammma and post
gamma enabling in intel_color_check to align with atomic.

v8: Addressed Maarten's review comments.

Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1549893025-21837-3-git-send-email-uma.shankar@intel.com