mac80211: Use appropriate debug wrapper

ieee80211_sta_expire will be called by both IBSS and mesh
interfaces to account for inactive stations, so it would be more
appropriate to use sta_dbg instead of ibss_dbg.

Signed-off-by: Mohammed Shafi Shajakhan <mohammed@qca.qualcomm.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>