Linux 5.2 rc4

No, I'm not confused, and I haven't lost track of what day it is, I do
actually know that it's still Saturday here, not Sunday, and I'm just
doing rc4 a bit early because I'll be on an airplane during my normal
release time. And while I've done releases on airports and airplanes
before, I looked at my empty queue of pull requests and went "let's
just do it now".

We've had a fairly calm release so far, and on the whole that seems to
hold. rc4 isn't smaller than rc3 was (it's a bit bigger), but rc3 was
fairly small, so the size increase isn't all that worrisome. I do hope
that we'll start actually shrinking now, though.

The SPDX conversions do continue to stand out, and make the diffstat a
bit noisy. They don't affect actual code, so it's not like we should
have any issues with them, but it makes the patch statistics look a
bit odd. There's just a lot more files changed than is normal in the
rc phase, and 90+% of that changed file list comes from the SPDX
changes. Of course, the SPDX changes also account for 95+% percent of
the removed lines in rc4, which is why I'm not complaining. It does
make the copyright boilerplates be a lot more legible to humans too,
not just for scripting.

But it does make the diff almost impossible to read, because so much
of it is due to just the SPDX notice work. You can use interdiff to
skip the SPDX stuff if you really want to, and if you do, you'll see
the usual arch updates (arm64, mips, parisc, nds32) various random
drivers updates (gpu stands out, some rdma), networking fixes,
filesystems (ceph, ovlfs, xfs). And misc other stuff.

But the appended shortlog is probably even more informative. None of
it really looks all that gnarly.