wifi: rtl8xxxu: Fix the channel width reporting

The gen 2 chips RTL8192EU and RTL8188FU periodically send the driver
reports about the TX rate, and the driver passes these reports to
sta_statistics. The reports from RTL8192EU may or may not include the
channel width. The reports from RTL8188FU do not include it.

Only access the c2h->ra_report.bw field if the report (skb) is big
enough.

The other problem fixed here is that the code was actually never
changing the channel width initially reported by
rtl8xxxu_bss_info_changed because the value of RATE_INFO_BW_20 is 0.

Fixes: 0985d3a4 ("rtl8xxxu: Feed current txrate information for mac80211")
Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
Reviewed-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/5b41f1ae-72e7-6b7a-2459-b736399a1c40@gmail.com

drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c

@@ -5569,7 +5569,6 @@ static void rtl8xxxu_c2hcmd_callback(struct work_struct *work)
 			rarpt->txrate.flags = 0;
 			rate = c2h->ra_report.rate;
 			sgi = c2h->ra_report.sgi;
-			bw = c2h->ra_report.bw;
 
 			if (rate < DESC_RATE_MCS0) {
 				rarpt->txrate.legacy =
@@ -5586,8 +5585,13 @@ static void rtl8xxxu_c2hcmd_callback(struct work_struct *work)
 						RATE_INFO_FLAGS_SHORT_GI;
 				}
 
-				if (bw == RATE_INFO_BW_20)
-					rarpt->txrate.bw |= RATE_INFO_BW_20;
+				if (skb->len >= offsetofend(typeof(*c2h), ra_report.bw)) {
+					if (c2h->ra_report.bw == RTL8XXXU_CHANNEL_WIDTH_40)
+						bw = RATE_INFO_BW_40;
+					else
+						bw = RATE_INFO_BW_20;
+					rarpt->txrate.bw = bw;
+				}
 			}
 			bit_rate = cfg80211_calculate_bitrate(&rarpt->txrate);
 			rarpt->bit_rate = bit_rate;