drm/doc: use preferred struct reference in kernel-doc

sed -e 's/\( \* .*\)struct &\([_a-z]*\)/\1\&struct \2/' -i

Originally I wasnt a friend of this style because I thought a
line-break between the "&struct" and "foo" part would break it. But a
quick test shows that " * &struct \n * foo\n" works pefectly well with
current kernel-doc. So time to mass-apply these changes!

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1483044517-5770-6-git-send-email-daniel.vetter@ffwll.ch

include/drm/drm_auth.h

@@ -48,7 +48,7 @@ struct drm_master {
 	 */
 	char *unique;
 	/**
-	 * @unique_len: Length of unique field. Protected by struct &drm_device
+	 * @unique_len: Length of unique field. Protected by &struct drm_device
 	 * master_mutex.
 	 */
 	int unique_len;