mac80211: check DSSS params IE length in parser

It's always just one byte, so check for that and
remove the length field from the parser struct.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/ibss.c b/net/mac80211/ibss.c
index 5ab32e2..2a0b218 100644
--- a/net/mac80211/ibss.c
+++ b/net/mac80211/ibss.c
@@ -463,7 +463,7 @@
 	struct ieee80211_supported_band *sband = local->hw.wiphy->bands[band];
 	bool rates_updated = false;
 
-	if (elems->ds_params && elems->ds_params_len == 1)
+	if (elems->ds_params)
 		freq = ieee80211_channel_to_frequency(elems->ds_params[0],
 						      band);
 	else