drm/i915/icl: Enable ICL Pipe CSC block

Enable ICL pipe csc hardware. CSC block is enabled
in CSC_MODE register instead of PLANE_COLOR_CTL.

ToDO: Extend the ABI to accept 32 bit coefficient values
instead of 16bit for future platforms.

v2: Addressed Maarten's review comments.

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

v4: Addressed Matt's review comments.

v5: Addressed Ville's review comments.

v6: Separated pipe output csc programming from regular csc.

v7: Rebase

Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@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/1549893025-21837-4-git-send-email-uma.shankar@intel.com