xfrm: call xfrm_dev_policy_delete when kill policy

xfrm_policy_kill() is called at different places to delete xfrm
policy. It will call xfrm_pol_put(). But xfrm_dev_policy_delete() is
not called to free the policy offloaded to hardware.

The three commits cited here are to handle this issue by calling
xfrm_dev_policy_delete() outside xfrm_get_policy(). But they didn't
cover all the cases. An example, which is not handled for now, is
xfrm_policy_insert(). It is called when XFRM_MSG_UPDPOLICY request is
received. Old policy is replaced by new one, but the offloaded policy
is not deleted, so driver doesn't have the chance to release hardware
resources.

To resolve this issue for all cases, move xfrm_dev_policy_delete()
into xfrm_policy_kill(), so the offloaded policy can be deleted from
hardware when it is called, which avoids hardware resources leakage.

Fixes: 919e43fa ("xfrm: add an interface to offload policy")
Fixes: bf06fcf4 ("xfrm: add missed call to delete offloaded policies")
Fixes: 982c3aca ("xfrm: delete offloaded policy")
Signed-off-by: Jianbo Liu <jianbol@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>