rt2x00: rt2800lib: fix antenna configuration for RT3593

On the RT3593 chipset, BBP register 86 must be
configured by different values based on the RX
antenna numbers.

Configure this register from the 'rt2800_config_ant'
function.

Based on the Ralink DPO_RT5572_LinuxSTA_2.6.0.1_20120629
driver.

Reference:
  RT3593_CONFIG_SET_BY_ANTENNA in include/chip/rt3593.h
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Acked-by: Stanislaw Gruszka <stf_xl@wp.pl>
Acked-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2800lib.c

@@ -1803,6 +1803,13 @@ void rt2800_config_ant(struct rt2x00_dev *rt2x00dev, struct antenna_setup *ant)
 
 	rt2800_bbp_write(rt2x00dev, 3, r3);
 	rt2800_bbp_write(rt2x00dev, 1, r1);
+
+	if (rt2x00_rt(rt2x00dev, RT3593)) {
+		if (ant->rx_chain_num == 1)
+			rt2800_bbp_write(rt2x00dev, 86, 0x00);
+		else
+			rt2800_bbp_write(rt2x00dev, 86, 0x46);
+	}
 }
 EXPORT_SYMBOL_GPL(rt2800_config_ant);