CVE-2024-36903 ipv6: Fix potential uninit-value access in __ip6_make_skb()

In the Linux kernel, the following vulnerability has been resolved: ipv6: Fix potential uninit-value access in ip6makeskb As it was done in commit fc1092f51567 "ipv4: Fix uninit-value access in ipmakeskb" for IPv4, check FLOWIFLAGKNOWNNH on fl6-flowi6flags instead of testing HDRINCL on the socket...