Removed old hotplug install which is no longer used at all and

Removed old hotplug install which is no longer used at all and
just left udev as the only hotplug mechanism. I've also added
an option to disable the installation of the firmware. This
is useful for debian or ubuntu packages where the firmware
is now provided by a package accompanying the staging kernel.
All usbdux files are included in the kernel firmware packages.
Package maintainers should use the --disable-firmware option.