drm: Add kernel-doc for drm_fb_helper_funcs->initial_config

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

include/drm/drm_fb_helper.h

@@ -57,6 +57,7 @@ struct drm_fb_helper_surface_size {
  * @fb_probe: - Driver callback to allocate and initialize the fbdev info
  * 		structure. Futhermore it also needs to allocate the drm
  * 		framebuffer used to back the fbdev.
+ * @initial_config: - Setup an initial fbdev display configuration
  *
  * Driver callbacks used by the fbdev emulation helper library.
  */