drm/i915: Clean up cursor defines

Use MCURSOR_ instead of CURSOR_ as the prefix for the non-845/865
cursor defines consistently, and move the pipe CSC enable bit next
to the other non-845/865 cursor defines.

v2: Take care of gvt uses as well
v3: Another gvt use popped up

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180131143709.875-1-ville.syrjala@linux.intel.com
Reviewed-by: Mika Kahola <mika.kahola@intel.com> #v2