This reverts commit b0355dbb.

The reverted commit clears the secpath on packets received via xfrm interfaces
to support nested IPsec tunnels. This breaks Netfilter policy matching using
xt_policy in the FORWARD chain, as the secpath is missing during forwarding.
Additionally, Benedict Wong reports that it breaks Transport-in-Tunnel mode.

Fix this regression by reverting the commit until we have a better approach
for nested IPsec tunnels.

Fixes: b0355dbb ("Fix XFRM-I support for nested ESP tunnels")
Link: https://lore.kernel.org/netdev/20230412085615.124791-1-martin@strongswan.org/Signed-off-by: Martin Willi <martin@strongswan.org>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>