wlcore: change warn on missing lock in wlcore_queue_xx funcs

On !CONFIG_SMP builds spin_is_locked always returns 0. Assert the
locking using assert_spin_locked, which is written to behave correctly
in all cases.

Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>