staging: rtl8192u: make in r819xU_cmdpkt.c some local functions static

Make some local functions static.

Fix sparse warnings in r819xU_cmdpkt.c

drivers/staging/rtl8192u/r819xU_cmdpkt.c:185:6: warning: symbol 'cmdpkt_beacontimerinterrupt_819xusb' was not declared. Should it be static?
Signed-off-by: Ana Rey <anarey@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8192u/r819xU_cmdpkt.c

@@ -182,7 +182,7 @@ static void cmpk_handle_tx_feedback(struct net_device *dev, u8 *pmsg)
 
 }
 
-void cmdpkt_beacontimerinterrupt_819xusb(struct net_device *dev)
+static void cmdpkt_beacontimerinterrupt_819xusb(struct net_device *dev)
 {
 	struct r8192_priv *priv = ieee80211_priv(dev);
 	u16 tx_rate;