[Skiboot] Preparing for skiboot-5.0

[Stewart Smith]

Hi all,

In about a week I'm thinking is a good time to tag skiboot-5.0

It will have a bunch of FSP, BMC and OpenPower related code and has a
bunch of extra features and capabilities over skiboot-4.1.1.

In the time up until then, any extra testing is *very* welcome.

I'm thinking the likely set of patches to be applied that aren't already
are the ones currently on the list - see
https://patchwork.ozlabs.org/project/skiboot/list/ along with any other
patches that are important to get in.