staging: usbip: change the busid size

Change busid size to correspond with SYSFS_BUS_ID_SIZE, which was
already being used in most cases. This eliminates the need to define
BUS_ID_SIZE in the userspace code.

Signed-off-by: matt mooney <mfm@muteddisk.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>