drm/i915/icl: Define Plane Input CSC Coefficient Registers

Defined the plane input csc coefficient registers and macros.
6 registers are used to program a total of 9 coefficients,
added macros to define each of them for all the planes
supporting the feature on pipes. On ICL, bottom 3 planes
have this capability.

v2: Segregated the register macro definition as separate patch
as per Maarten's suggestion.

v3: Removed a redundant 3rd Pipe register definition and
simplified the equally spaced register definition by adding an
offset as per Matt's comment.

v4: No Change

v5: Renamed the register Macro as per Matt's suggestion.

v6: No Change

v7: No Change

v8: No Change

v9: No Change

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/1541099420-12419-2-git-send-email-uma.shankar@intel.com