wl12xx: use 1 spare block in all cases

Remove support for firmwares that require 2 spare blocks for packet TX
(and delete the WL12XX_QUIRK_USE_2_SPARE_BLOCKS quirk definition)

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