MIPS: bpf: Add SEEN_SKB to flags when looking for the PKT_TYPE

The SKF_AD_PKTTYPE uses the skb pointer so make sure it's in the
flags so it will be initialized in time.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Daniel Borkmann <dborkman@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: netdev@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/7125/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>