xfrm: Fix skb double-free in xfrm_dev_direct_output()

A return value other than 1 from local_out() means that the skb has been
consumed or its ownership was transferred. xfrm_dev_direct_output()
nevertheless frees the skb on this path, causing a double-free when
netfilter drops the packet and invalidating any other owner.

Return the local_out() result directly, matching the ownership handling
in xfrm_output_resume().

Fixes: 5eddd76ec2fd ("xfrm: fix tunnel mode TX datapath in packet offload mode")
Signed-off-by: Sanghyun Park <sanghyun.park.cnu@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>