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

This is a partial revert of 7f26b3a7533b ("drivers/usb: Remove unnecessary
return's from void functions") as this hunk will vanish in USB tree completely.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
index a83a139..6fca870 100644
--- a/drivers/usb/musb/musb_gadget.c
+++ b/drivers/usb/musb/musb_gadget.c
@@ -829,6 +829,7 @@
 		DBG(3, "packet waiting for %s%s request\n",
 				musb_ep->desc ? "" : "inactive ",
 				musb_ep->end_point.name);
+	return;
 }
 
 /* ------------------------------------------------------------ */