wcn36xx: Fix HT40 capability for 2Ghz band

All wcn36xx controllers are supposed to support HT40 (and SGI40),
This doubles the maximum bitrate/throughput with compatible APs.

Tested with wcn3620 & wcn3680B.

Cc: stable@vger.kernel.org
Fixes: 8e84c25 ("wcn36xx: mac80211 driver for Qualcomm WCN3660/WCN3680 hardware")
Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1634737133-22336-1-git-send-email-loic.poulain@linaro.org

Author: Loic Poulain

drivers/net/wireless/ath/wcn36xx/main.c

@@ -135,7 +135,9 @@ static struct ieee80211_supported_band wcn_band_2ghz = {
 		.cap =	IEEE80211_HT_CAP_GRN_FLD |
 			IEEE80211_HT_CAP_SGI_20 |
 			IEEE80211_HT_CAP_DSSSCCK40 |
-			IEEE80211_HT_CAP_LSIG_TXOP_PROT,
+			IEEE80211_HT_CAP_LSIG_TXOP_PROT |
+			IEEE80211_HT_CAP_SGI_40 |
+			IEEE80211_HT_CAP_SUP_WIDTH_20_40,
 		.ht_supported = true,
 		.ampdu_factor = IEEE80211_HT_MAX_AMPDU_64K,
 		.ampdu_density = IEEE80211_HT_MPDU_DENSITY_16,