mac80211: debugfs: add file to disallow TDLS wider-bw

Sometimes we are interested in testing TDLS performance in a specific
width setting. Add the ability to disable the wider-band feature, thereby
allowing the TDLS channel width to be controlled by the BSS width.

Signed-off-by: Arik Nemtsov <arikx.nemtsov@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>