hid-related 5.2-rc1 boot hang

[Dave Hansen]

I have a system that works fine on 5.1.  When updating to 5.2-rc1, it
hangs at boot waiting on an instance of systemd-udevd.  The kernel
backtrace (https://photos.app.goo.gl/EV8rf7FofWouvdeE8) looks like it's
doing an finit_module() that dives into the hid code and is waiting on a
request_module().

This hang only occurs if I have a particular USB device inserted:

> Bus 001 Device 007: ID 046d:c52b Logitech, Inc. Unifying Receiver

Bisecting the issue points at this (unlikely to be the culprit) commit:

> [161f62cd07fde123fd52bf6d5b6fd6513cca968e] HID: macally: Add support for Macally ikey keyboard

This bisect result is probably just a bisect artifact.  The first real,
bad commit is a merge commit: 63b6f0b827d.  This commit merges a bunch
of stuff, but includes changes to the hid request_module() code and to
the logitech-hidpp which is the driver for the above device.

I also have a picture of the hang which includes __request_module()
dumping out the string it is passed:

	https://photos.app.goo.gl/tUETiCBZHJfKqWPu8

This is easy enough to work around, and the system works fine if I just
unplug the Logitech device and plug it in after boot.  But, it would be
nice to figure out what's going wrong.  I guess it could easily be some
interaction between systemd, the driver and the request_module() ordering.