wl12xx: Revert "wl12xx: schedule TX packets according to FW occupancy"

This does not make sense in fw >= 6/7.3.0.0.75 (wl127x/wl128x) -
we don't use Tx blocks to measure FW occupancy anymore.

This reverts commit 9e374a37.

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