Kernel prepatch 5.16-rc1

The 5.16-rc1 kernel prepatch is out and the
merge window is closed for this cycle.

Anyway, it's not a huge release, although it's also not a
remarkably small one like 5.15 was (ok, 'remarkably small' is
relative, when even such small releases have 10k+
commits).. There's a bit of everything in here, and you can look to
the appended mergelog for some kind of flavor, but I guess the
folio work is worth mentioning, since it's an unusually core thing
that we don't tend to see most releases.