CVE-2026-99033 net/packet: guard the ll header push in packet_rcv_spkt()

In the Linux kernel, the following vulnerability has been resolved: net/packet: guard the ll header push in packetrcvspkt packetrcvspkt restores the link layer header with skbpushskb, skb-data - skbmacheaderskb; That subtraction is only meaningful when the device actually has a link layer header...