USB: misc: yurex: fix race between read and write

The write code path touches the bbu member in a non atomic manner
without taking the spinlock. Fix it.

The bug is as old as the driver.

Signed-off-by: Oliver Neukum <oneukum@suse.com>
CC: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240912132126.1034743-1-oneukum@suse.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>