The comparison of len < 0 is always false because len is a size_t. Fix
this by making len a ssize_t instead.
Addresses-Coverity: ("Unsigned compared against 0")
Fixes: d395381909a3 ("netdevsim: Add max_vfs to bus_dev")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
 {
        struct nsim_bus_dev *nsim_bus_dev = file->private_data;
        char buf[11];
-       size_t len;
+       ssize_t len;
 
        len = snprintf(buf, sizeof(buf), "%u\n", nsim_bus_dev->max_vfs);
        if (len < 0)