mac80211: remove iwlwifi specific workaround NDPs of null_response

Remove the remaining workaround that is not removed by the
commit e41eb3e4 ("mac80211: remove iwlwifi specific workaround
that broke sta NDP tx")

Fixes: 41cbb0f5 ("mac80211: add support for HE")
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://lore.kernel.org/r/20210623134826.10318-1-pkshih@realtek.com


Signed-off-by: Johannes Berg <johannes.berg@intel.com>