mac80211: do not allow HT/VHT IEs in 6 GHz mesh mode

As HT/VHT elements are not allowed in 6 GHz band, do not include
them in mesh beacon template formation.

Signed-off-by: Rajkumar Manoharan <rmanohar@codeaurora.org>
Link: https://lore.kernel.org/r/1589399105-25472-9-git-send-email-rmanohar@codeaurora.org
Link: https://lore.kernel.org/r/20200528193455.76796-2-johannes@sipsolutions.net


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