drm/i915: Make the DRRS debugfs contents more consistent

The stuff in the DRRS debugs is currently a hodgepode mix
of camelcase, lowercase, spaces, undescores, you name it.
Convert over to a reasonably common style.

Also move the busy bits thing to be the last sine it's
generally the least interesting thing in there.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221003113249.16213-3-ville.syrjala@linux.intel.com