xfrm: Pass flowi_oif or l3mdev as oif to xfrm_dst_lookup

The commit referenced in the Fixes tag no longer changes the
flow oif to the l3mdev ifindex. A xfrm use case was expecting
the flowi_oif to be the VRF if relevant and the change broke
that test. Update xfrm_bundle_create to pass oif if set and any
potential flowi_l3mdev if oif is not set.

Fixes: 40867d74

 ("net: Add l3mdev index to flow struct and avoid oif reset for port devices")
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>