drm/vtables: Fix typo

The callback is named .atomic_check, not .atomc_check.
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NThierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170901144042.6023-1-thierry.reding@gmail.com

include/drm/drm_modeset_helper_vtables.h

@@ -314,7 +314,7 @@ struct drm_crtc_helper_funcs {
 	 * implementation in drm_atomic_helper_check().
 	 *
 	 * When using drm_atomic_helper_check_planes() this hook is called
-	 * after the &drm_plane_helper_funcs.atomc_check hook for planes, which
+	 * after the &drm_plane_helper_funcs.atomic_check hook for planes, which
 	 * allows drivers to assign shared resources requested by planes in this
 	 * callback here. For more complicated dependencies the driver can call
 	 * the provided check helpers multiple times until the computed state