iwlwifi: support DSSS/CCK mode in 40 MHz

All hardware after 4965 supports this. It's likely that
it wasn't set because for 4965 it was irrelevant (HT is
only supported on 5 GHz there) and then never updated.
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/iwlwifi/iwl-eeprom-parse.c

@@ -749,7 +749,7 @@ void iwl_init_ht_hw_capab(const struct iwl_cfg *cfg,
 	}
 
 	ht_info->ht_supported = true;
-	ht_info->cap = 0;
+	ht_info->cap = IEEE80211_HT_CAP_DSSSCCK40;
 
 	if (iwlwifi_mod_params.amsdu_size_8K)
 		ht_info->cap |= IEEE80211_HT_CAP_MAX_AMSDU;