uas: replace WARN_ON_ONCE() with lockdep_assert_held()

on some architecture spin_is_locked() always return false in
uniprocessor configuration and therefore it would be advise
to replace with lockdep_assert_held().

Signed-off-by: Sanjeev Sharma <Sanjeev_Sharma@mentor.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>