drm/i915: s/_CURSOR2/_MMIO_CURSOR2//

The other similar macros have the _MMIO prefix, so give
it also to _CURSOR2.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220623130900.26078-6-ville.syrjala@linux.intel.com


Reviewed-by: Jani Nikula <jani.nikula@intel.com>