Merge branch 'erspan-always-reports-output-key-to-userspace'

Lorenzo Bianconi says:

====================
erspan: always reports output key to userspace

Erspan protocol relies on output key to set session id header field.
However TUNNEL_KEY bit is cleared in order to not add key field to
the external GRE header and so the configured o_key is not reported
to userspace.
Fix the issue adding TUNNEL_KEY bit to the o_flags parameter dumping
device info
====================

Signed-off-by: David S. Miller <davem@davemloft.net>