drm/i915: Use intel_ types more consistently for color management code (v2)

Try to be more consistent about intel_* types rather than drm_* types
for lower-level driver functions.  While we're at it, let's also be more
consistent with state variable naming (half of the platforms use the
name 'state' whereas the other half used 'crtc_state').

While we're touching these variables, let's also be more consistent
about always naming the intel_crtc_state's "crtc_state" rather than
"state" so that different platform types aren't using different naming
conventions.

v2:
 - s/state/crtc_state/ for consistency between platform types (Ville)
 - Drop the crtc parameter to intel_color_check(); we can just pull that
   out of the state object.

Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181210215415.19854-2-matthew.d.roper@intel.com