mei: mei_hbm_dispatch() returns void

Building hbm.o for v3.13.2 triggers a GCC warning:
    drivers/misc/mei/hbm.c: In function 'mei_hbm_dispatch':
    drivers/misc/mei/hbm.c:596:3: warning: 'return' with a value, in function returning void [enabled by default]
       return 0;
       ^

GCC is correct, obviously. So let's return void instead of zero here.
Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Acked-by: Tomas Winkler <tomas.winkler@intel.com>
Cc: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/mei/hbm.c

@@ -593,7 +593,7 @@ void mei_hbm_dispatch(struct mei_device *dev, struct mei_msg_hdr *hdr)
 	 */
 	if (dev->hbm_state == MEI_HBM_IDLE) {
 		dev_dbg(&dev->pdev->dev, "hbm: state is idle ignore spurious messages\n");
-		return 0;
+		return;
 	}
 
 	switch (mei_msg->hbm_cmd) {