USB: disable USB_MULTITHREAD_PROBE

Disable the USB_MULTITHREAD_PROBE option because it causes crashes on
people's machines and they never remember to actually read the config
help files.

No one likes this, everyone hates it, I'm going to go eat worms...

The full logic will be ripped out later.

Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>