rt2800: fix TX_PIN_CFG setting for non MT7620 chips

Since commit 41977e86c984 ("rt2x00: add support for MT7620") we do not
initialize TX_PIN_CFG setting. This cause breakage at least on some
RT3573 devices. To fix the problem patch restores previous behaviour
for non MT7620 chips.

Fixes: 41977e86c984 ("rt2x00: add support for MT7620")
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1480829
Reported-and-tested-by: Jussi Eloranta <jussi.eloranta@csun.edu>
Cc: Daniel Golle <daniel@makrotopia.org>
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Daniel Golle <daniel@makrotopia.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/ralink/rt2x00/rt2800lib.c

@@ -3702,7 +3702,10 @@ static void rt2800_config_channel(struct rt2x00_dev *rt2x00dev,
 	if (rt2x00_rt(rt2x00dev, RT3572))
 		rt2800_rfcsr_write(rt2x00dev, 8, 0);
 
-	tx_pin = rt2800_register_read(rt2x00dev, TX_PIN_CFG);
+	if (rt2x00_rt(rt2x00dev, RT6352))
+		tx_pin = rt2800_register_read(rt2x00dev, TX_PIN_CFG);
+	else
+		tx_pin = 0;
 
 	switch (rt2x00dev->default_ant.tx_chain_num) {
 	case 3: