linsysfs: create /sys/bus/ and /sys/subsystem/

This looks like a no-op, but it prevents udevadm(8) with failing
loudly, which in turn unbreaks installation of libfprint-2-2, which
in Focal is a dependency for make-4.2.1-1.2.

One might wonder why installing a build utility involves messing
with device handling...

Sponsored By: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D29133