drm/i915: reorder and reindent the register choosing helper wrappers

Try to make it slightly less of an eye sore. No functional changes.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181031110453.12722-3-jani.nikula@intel.com