doc: update release notes for IPsec
doc: update release notes for IPsec

Update release notes for recently supported features in IPsec library and
IPsec Security Gateway application.

Signed-off-by: Bernard Iremonger <233eeff376ad0c06f66f06c5522ea3c4feb30d3b@intel.com>
Acked-by: Akhil Goyal <74d7c4c993a22c1d4f60c46ff3d95c969a24a25c@nxp.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk