cfg80211: regulatory: introduce NL80211_RRF_AUTO_BW rule flag

Introduce NL80211_RRF_AUTO_BW rule flag. If this flag set
maximum available bandwidth should be calculated base on
contiguous rules and wider channels will be allowed to cross
multiple contiguous/overlapping frequency ranges.

In case of old kernels maximum bandwidth from regulatory
rule will be used, while there is no NL80211_RRF_AUTO_BW flag.

This fixes the previous commit 97524820
("cfg80211: regulatory introduce maximum bandwidth calculation")
which was found to be a problem for userspace API compatibility.

Signed-off-by: Janusz Dziedzic <janusz.dziedzic@tieto.com>
[edit commit log, use sizeof()]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

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