bonding: add common function to check ipsec device

bonding: add common function to check ipsec device

This patch adds a common function to check the status of IPSec devices.
This function will be useful for future implementations, such as IPSec ESN
and state offload callbacks.

Suggested-by: Nikolay Aleksandrov <razor@blackwall.org>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Acked-by: Jay Vosburgh <jv@jvosburgh.net>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>