LinuxKPI: 802.11: implement cfg80211_get_ies_channel_number()
Using the previous changes implement cfg80211_get_ies_channel_number()
either based on DSPARMS (or for the future HTINFO).
Sponsored by: The FreeBSD Foundation
(cherry picked from commit 13d87d92e401523f8d8e817720d40dc31cdfa444)