drm/kms-helpers: Use recommened kerneldoc for struct member refs

I just learned that &struct_name.member_name works and looks pretty
even. It doesn't (yet) link to the member directly though, which would
be really good for big structures or vfunc tables (where the
per-member kerneldoc tends to be long).

Also some minor drive-by polish where it makes sense, I read a lot
of docs ...

v2: Comments from Gustavo.

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Rewiewed-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170125062657.19270-2-daniel.vetter@ffwll.ch
diff --git a/include/drm/drm_simple_kms_helper.h b/include/drm/drm_simple_kms_helper.h
index d138d08..fffbb95 100644
--- a/include/drm/drm_simple_kms_helper.h
+++ b/include/drm/drm_simple_kms_helper.h
@@ -77,9 +77,9 @@
 	/**
 	 * @prepare_fb:
 	 *
-	 * Optional, called by &struct drm_plane_helper_funcs ->prepare_fb .
-	 * Please read the documentation for the ->prepare_fb hook in
-	 * &struct drm_plane_helper_funcs for more details.
+	 * Optional, called by &drm_plane_helper_funcs.prepare_fb.  Please read
+	 * the documentation for the &drm_plane_helper_funcs.prepare_fb hook for
+	 * more details.
 	 */
 	int (*prepare_fb)(struct drm_simple_display_pipe *pipe,
 			  struct drm_plane_state *plane_state);
@@ -87,9 +87,9 @@
 	/**
 	 * @cleanup_fb:
 	 *
-	 * Optional, called by &struct drm_plane_helper_funcs ->cleanup_fb .
-	 * Please read the documentation for the ->cleanup_fb hook in
-	 * &struct drm_plane_helper_funcs for more details.
+	 * Optional, called by &drm_plane_helper_funcs.cleanup_fb.  Please read
+	 * the documentation for the &drm_plane_helper_funcs.cleanup_fb hook for
+	 * more details.
 	 */
 	void (*cleanup_fb)(struct drm_simple_display_pipe *pipe,
 			   struct drm_plane_state *plane_state);