b43: remove WDS code

The ability to reach this code was hidden behind
CONFIG_WIRELESS_WDS, which was just removed. Clean
up the driver accordingly.

Link: https://lore.kernel.org/r/20201109105103.f1d9486874fc.I081f5771478ec3a45c2a22c158ed9aea661336e1@changeid


Acked-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>