continuous release notes

Hi,

In order to provide a good release notes with little efforts, we have to update this file continuously:
http://dpdk.org/browse/dpdk/tree/doc/guides/rel_notes/release_2_2.rst

It means each patch adding a new feature or fixing a serious bug of a previous release, must include a new item in the release notes.

We missed it for some previous patch:
17e01e3 i40e: fix base driver allocation when not using first numa node 45e73f4 ixgbe: remove burst size restriction of vector Rx b7fcd13 ixgbe: fix X550 DCB
7d49e0f hash: fix memory allocation of cuckoo key table 79db649 eal/linux: fix epoll timeout

Thanks for taking care.