[coreboot] coreboot release 4.8 - Targeting May 15.

[Martin Roth]

The coreboot 4.8 release is planned for May 15.  That's the day that we'll
choose the commit to base the release on and create the release tag in
git.  The tarballs will be available on the website shortly afterwards.

For anyone who feels like contributing to the release notes, you can work
on them here:
https://pads.ccc.de/yGXyCFe7g7
I've added the list of commits up to today in the document, below the
release notes section.

It would be helpful if people could test their boards and upload the
results board-status repository.  This lets everyone know that the code for
that board, processor, and chipset is still working in the current coreboot
tree.

As always, thanks to everyone involved in coreboot.  Your work is greatly
appreciated.

Martin