mei: fix kernel-doc warnings

Add missed parameters descriptions and return values descriptions

Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/misc/mei/hw.h b/drivers/misc/mei/hw.h
index ea8de2a..16fef6d 100644
--- a/drivers/misc/mei/hw.h
+++ b/drivers/misc/mei/hw.h
@@ -109,6 +109,8 @@
  * @MEI_HBMS_NOT_ALLOWED       : operation not allowed
  * @MEI_HBMS_ALREADY_STARTED   : system is already started
  * @MEI_HBMS_NOT_STARTED       : system not started
+ *
+ * @MEI_HBMS_MAX               : sentinel
  */
 enum mei_hbm_status {
 	MEI_HBMS_SUCCESS           = 0,