Correct the use of snprintf in owinterface_add

The origin size value of snprintf in owinterface_add was ETH_ALEN, if
the string size is too large, it will only allow ETH_ALEN - 1 characters
to be copied into the buffer.

However, the buffer starts from location inf_name + 1 and the last
character must be '\0', which means that the buffer only has at most
ETH_ALEN - 2 characters space left.

So the size value in snprintf of owinterface_add should be ETH_ALEN - 1

Author: vax-r

vwifi.c

@@ -1216,7 +1216,7 @@ static struct wireless_dev *owinterface_add(struct wiphy *wiphy, int if_idx)
      * address (the first byte of multicast addrs is odd).
      */
     char intf_name[ETH_ALEN] = {0};
-    snprintf(intf_name + 1, ETH_ALEN, "%s%d", NAME_PREFIX, if_idx);
+    snprintf(intf_name + 1, ETH_ALEN - 1, "%s%d", NAME_PREFIX, if_idx);
 
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 15, 0)
     eth_hw_addr_set(vif->ndev, intf_name);