libertas: Add missing sentinel at end of if_usb.c fw_table

This sentinel tells the firmware loading process when to stop.

Reported-and-tested-by: syzbot+98156c174c5a2cad9f8f@syzkaller.appspotmail.com
Signed-off-by: Kevin Easton <kevin@guarana.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/marvell/libertas/if_usb.c

@@ -50,7 +50,8 @@ static const struct lbs_fw_table fw_table[] = {
 	{ MODEL_8388, "libertas/usb8388_v5.bin", NULL },
 	{ MODEL_8388, "libertas/usb8388.bin", NULL },
 	{ MODEL_8388, "usb8388.bin", NULL },
-	{ MODEL_8682, "libertas/usb8682.bin", NULL }
+	{ MODEL_8682, "libertas/usb8682.bin", NULL },
+	{ 0, NULL, NULL }
 };
 
 static const struct usb_device_id if_usb_table[] = {