openvswitch: upgrade to version 2.3.1
Release notes here:
https://github.com/openvswitch/ovs/blob/v2.3.1/NEWS
Remove patch (included in 2.3.1):
0005-datapath-backport___ip_select_ident_function.patch
Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>