udev: allow firmware requests to bypass the dependency tracking

udev: allow firmware requests to bypass the dependency tracking

The removal of the TIMEOUT= handling in udevd put firmware requests into the
devpath parent/child dependency tracking. Drivers which block in module_init()
asking userspace for firmware ran into a 30 sec device timeout.

The whole firmware loading willl hopefully move into the kernel and
the fragile-since-day-one fake async driver-core device dance involving
udev can be retired:
  http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commit;h=abb139e75c2cdbb955e840d6331cb5863e409d0e