Revert "drivers/usb: Remove unnecessary return's from void functions" for musb gadget

This is a partial revert of 7f26b3a7 ("drivers/usb: Remove unnecessary
return's from void functions") as this hunk will vanish in USB tree completely.
Reported-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

drivers/usb/musb/musb_gadget.c

@@ -829,6 +829,7 @@ void musb_g_rx(struct musb *musb, u8 epnum)
 		DBG(3, "packet waiting for %s%s request\n",
 				musb_ep->desc ? "" : "inactive ",
 				musb_ep->end_point.name);
+	return;
 }
 
 /* ------------------------------------------------------------ */