mac80211: sync dtim_count to TSF

On starting a mesh or AP BSS, the interface dtim_count
countdown should match that of the driver TSF.

Signed-off-by: Thomas Pedersen <twpedersen@gmail.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/debugfs_netdev.c

@@ -474,6 +474,7 @@ static ssize_t ieee80211_if_parse_tsf(
 		}
 	}
 
+	ieee80211_recalc_dtim(local, sdata);
 	return buflen;
 }
 IEEE80211_IF_FILE_RW(tsf);