strongswan: security bump to version 5.2.2

Fixes CVE-2014-9221 - denial-of-service vulnerability triggered by an
IKEv2 Key Exchange payload that contains the Diffie-Hellman group 1025.

Also add hash file.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>