rt2800: status based rate flags for nomatch case

We use skb_desc->tx_rate_flags from entry as rate[].flags even if
skb does not match status. Patch corrects flags and also fixes
mcs for legacy rates.

rt2800_rate_from_status() is based on Felix's mt76
mt76x2_mac_process_tx_rate() function.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/ralink/rt2x00/rt2800.h

@@ -1760,6 +1760,8 @@
 #define TX_STA_FIFO_WCID		FIELD32(0x0000ff00)
 #define TX_STA_FIFO_SUCCESS_RATE	FIELD32(0xffff0000)
 #define TX_STA_FIFO_MCS			FIELD32(0x007f0000)
+#define TX_STA_FIFO_BW			FIELD32(0x00800000)
+#define TX_STA_FIFO_SGI			FIELD32(0x01000000)
 #define TX_STA_FIFO_PHYMODE		FIELD32(0xc0000000)
 
 /*