Kernel prepatch 5.1-rc1

Linus has released 5.1-rc1 and closed the
merge window for this development cycle. 'A somewhat recent
development is how the tools/testing/ updates have been quite noticeable
lately. That's not new to the 5.1 merge window, it's been going on for a
while, but it's maybe just worth a mention that we have more new selftest
changes than we have architecture updates, for example. The documentation
subdirectory is also quite noticeable.'