package/easy-rsa: bump to version 3.1.0
Update hash of gpl-2.0.txt (new line removed)
https://github.com/OpenVPN/easy-rsa/releases/tag/v3.1.0
https://github.com/OpenVPN/easy-rsa/blob/v3.1.0/ChangeLog
Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>