mac80211: upgrade BW of TDLS peers when possible

Define a station chandef, to be used for wider-bw TDLS peers. When both
peers support the feature, upgrade the channel bandwidth to the maximum
allowed by both peers and regulatory. Currently widths up to 80MHz are
supported in the 5GHz band.

When a TDLS peer connects/disconnects recalculate the channel type of the
current chanctx.
Make the chanctx width calculation consider wider-bw TDLS peers and
similarly fix the max_required_bw calculation for the chanctx min_def.
Since the sta->bandwidth is calculated only later on, take
bss_conf.chandef.width as the minimal width for station interface.

Set the upgraded channel width in the VHT-operation set during TDLS setup.

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>