bpf: Allow cgroup sock filters to use get_current_uid_gid helper

Allow BPF programs run on sock create to use the get_current_uid_gid
helper. IPv4 and IPv6 sockets are created in a process context so
there is always a valid uid/gid

Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>