wifi: mac80211: sta_info: fix a missing kernel-doc struct element

struct link_sta_info has now a cur_max_bandwidth data:

	net/mac80211/sta_info.h:569: warning: Function parameter or member 'cur_max_bandwidth' not described in 'link_sta_info'

Copy the meaning from struct sta_info, documenting it.
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Link: https://lore.kernel.org/r/37d898634bb30776442a33833c48cbb21c90ecc6.1656409369.git.mchehab@kernel.orgSigned-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/sta_info.h

@@ -517,6 +517,8 @@ struct ieee80211_fragment_cache {
  * @status_stats.last_ack_signal: last ACK signal
  * @status_stats.ack_signal_filled: last ACK signal validity
  * @status_stats.avg_ack_signal: average ACK signal
+ * @cur_max_bandwidth: maximum bandwidth to use for TX to the station,
+ *	taken from HT/VHT capabilities or VHT operating mode notification
  * @pub: public (driver visible) link STA data
  * TODO Move other link params from sta_info as required for MLD operation
  */