mac80211: fix HT-Control field reception for management frames

If we receive management frames with an HT-Control field, we cannot
parse them properly, as we assume a fixed length management header.

Since we don't even need the HTC field (for these frames, or really
at all), just remove it at the beginning of RX.

Reported-by: Haggai Abramovsky <haggai.abramovsky@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Link: https://lore.kernel.org/r/20200526143346.cf5ce70521c5.I333251a084ec4cfe67b7ef7efe2d2f1a33883931@changeid


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