mac80211: add missing length field increment when generating Radiotap header

The code generating the Tx Radiotap header when using tx_status_ext was
missing a field increment after setting the VHT bandwidth.

Fixes: 3d07ffca ("mac80211: add struct ieee80211_tx_status support to ieee80211_add_tx_radiotap_header")
Signed-off-by: John Crispin <john@phrozen.org>
Link: https://lore.kernel.org/r/20190807075949.32414-4-john@phrozen.orgSigned-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/status.c

@@ -412,6 +412,7 @@ ieee80211_add_tx_radiotap_header(struct ieee80211_local *local,
 			*pos = 0;
 			break;
 		}
+		pos++;
 
 		/* u8 mcs_nss[4] */
 		*pos = (status->rate->mcs << 4) | status->rate->nss;