staging: usbip: fix to prevent potentially using uninitialized spinlock

The stub_probe function can be called as soon as the stub_driver is
registered. This can lead to the busid_table_lock being used before it
is initialized. Moved calling the init_busid_table function (which
initalizes this spinlock) to be called earlier in the init function to
prevent this from happening.

Signed-off-by: Bart Westgeest <bart@elbrys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>