uwb: uwbd() is not freezable kthread

uwbd() calls try_to_freeze(), but the thread doesn't mark itself freezable
through set_freezable(), so the try_to_freeze() call is useless.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>