drivers/net/hamradio: Move a dereference below a NULL test

In each case, if the NULL test is necessary, then the dereference should be
moved below the NULL test.

The semantic patch that makes this change is as follows:
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@@
type T;
expression E;
identifier i,fld;
statement S;
@@

- T i = E->fld;
+ T i;
  ... when != E
      when != i
  if (E == NULL) S
+ i = E->fld;
// </smpl>
Signed-off-by: NJulia Lawall <julia@diku.dk>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/hamradio/mkiss.c

@@ -846,12 +846,13 @@ static int mkiss_ioctl(struct tty_struct *tty, struct file *file,
 	unsigned int cmd, unsigned long arg)
 {
 	struct mkiss *ax = mkiss_get(tty);
-	struct net_device *dev = ax->dev;
+	struct net_device *dev;
 	unsigned int tmp, err;
 
 	/* First make sure we're connected. */
 	if (ax == NULL)
 		return -ENXIO;
+	dev = ax->dev;
 
 	switch (cmd) {
  	case SIOCGIFNAME: