xfrm: fix rcu_read_unlock usage in xfrm_local_error

[ Upstream commit 46c0ef6e1eb95f619d9f62da4332749153db92f7 ]

In the xfrm_local_error, rcu_read_unlock should be called when afinfo
is not NULL. because xfrm_state_get_afinfo calls rcu_read_unlock
if afinfo is NULL.

Fixes: af5d27c4 ("xfrm: remove xfrm_state_put_afinfo")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>