Linux 5.5 rc6

Things have picked up a _bit_ after the holiday season, but it's still
pretty quiet. Not outrageously so: this could almost be a normal rc5,
just slightly calmer than usual.

Let's see how things go. I do suspect that this ends up being one of
those "rc8" releases, not because things look particularly bad right
now, but simply because the holiday season has meant that both the
testing side and the development side have been quiet. But who knows?
It's entirely possible that we'll just have a very quiet next two
weeks, and I go "there is no point in delaying things".

So nothing looks particularly worrisome, and normally I'd be very
happy with a quiet rc6. I just suspect that there's some pent-up work
still, and I'm left waiting for the other shoe to drop...

Anyway, rc6 is dominated mostly by drivers. There's a little bit of
everything there: networking perhaps stands out, but there's USB, GPU,
HID, MTD, sound, gpio, block and misc other driver updates there.

Outside of drivers, there's core networking, some minor arch updates
(ARC, RISC-V, one arm64 revert), some tracing fixes, and a set of
fixes for the clone3() system call

But all of it is pretty small, and nothing really looks scary at all.
Scan the shortlog below if you are into that, but otherwise just go
forth and test it out all,