wifi: mac80211: use for_each_chanctx_user_* in one more place

wifi: mac80211: use for_each_chanctx_user_* in one more place

for_each_chanctx_user_* is an iterator that visits all types of chanctx
users, including the (to be added) NAN channels, and not only the link.

ieee80211_get_chanctx_max_required_bw wasn't changed to use this new
iterator, do it now.

Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20260320101556.4691916c7877.I9660f3945f4dccdb6d41a06ec4e74161e5ac65a4@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>