batman-adv: access unicast_ttvn skb->data only after skb realloc

In the Linux kernel, the following vulnerability has been resolved: batman-adv: access unicast_ttvn skb->data only after skb realloc The pskb_may_pull() called by batadv_get_vid() could reallocate the buffer behind the skb. Variables which were pointing to the old buffer need to be reassigned to avoid an use-after-free. This was done correctly for the ethernet header but missed for the unicast_packet pointer.