staging: sbe-2t3e3: fix sparse warnings

warnings:
drivers/staging/sbe-2t3e3/netdev.c:24:5: warning: symbol 't3e3_ioctl' was not declared. Should it be static?
drivers/staging/sbe-2t3e3/netdev.c:85:5: warning: symbol 't3e3_open' was not declared. Should it be static?
drivers/staging/sbe-2t3e3/netdev.c💯5: warning: symbol 't3e3_close' was not declared. Should it be static?

Signed-off-by: Devendra Naga <devendra.aaru@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/sbe-2t3e3/netdev.c

@@ -21,7 +21,7 @@
 #include <linux/interrupt.h>
 #include "2t3e3.h"
 
-int t3e3_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
+static int t3e3_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
 {
 	struct channel *sc = dev_to_priv(dev);
 	int cmd_2t3e3, len, rlen;
@@ -82,7 +82,7 @@ static struct net_device_stats* t3e3_get_stats(struct net_device *dev)
 	return nstats;
 }
 
-int t3e3_open(struct net_device *dev)
+static int t3e3_open(struct net_device *dev)
 {
 	struct channel *sc = dev_to_priv(dev);
 	int ret = hdlc_open(dev);
@@ -97,7 +97,7 @@ int t3e3_open(struct net_device *dev)
 	return 0;
 }
 
-int t3e3_close(struct net_device *dev)
+static int t3e3_close(struct net_device *dev)
 {
 	struct channel *sc = dev_to_priv(dev);
 	hdlc_close(dev);