rose: Fix signedness issues wrt. digi count.

Just use explicit casts, since we really can't change the
types of structures exported to userspace which have been
around for 15 years or so.
Reported-by: NDan Rosenberg <dan.j.rosenberg@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/rose/af_rose.c

@@ -679,7 +679,7 @@ static int rose_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 	if (addr_len == sizeof(struct sockaddr_rose) && addr->srose_ndigis > 1)
 		return -EINVAL;
 
-	if (addr->srose_ndigis > ROSE_MAX_DIGIS)
+	if ((unsigned int) addr->srose_ndigis > ROSE_MAX_DIGIS)
 		return -EINVAL;
 
 	if ((dev = rose_dev_get(&addr->srose_addr)) == NULL) {
@@ -739,7 +739,7 @@ static int rose_connect(struct socket *sock, struct sockaddr *uaddr, int addr_le
 	if (addr_len == sizeof(struct sockaddr_rose) && addr->srose_ndigis > 1)
 		return -EINVAL;
 
-	if (addr->srose_ndigis > ROSE_MAX_DIGIS)
+	if ((unsigned int) addr->srose_ndigis > ROSE_MAX_DIGIS)
 		return -EINVAL;
 
 	/* Source + Destination digis should not exceed ROSE_MAX_DIGIS */