ar71xx: fix bad RX sensitivity on newer TL-WDR4300 boards

On recent TL-WDR4300 boards the external LNAs of the 2.4GHz
interface are connected to GPIO lines. Because these GPIO
lines are disabled by default, the RX sensitivity of the
device is quite bad.

Setup the GPIOs of the external LNAs to fix the issue.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@39392 3c298f89-4303-0410-b956-a3cf2f4a3e73

target/linux/ar71xx/files/arch/mips/ath79/mach-tl-wdr4300.c

@@ -37,6 +37,9 @@
 #define WDR4300_GPIO_BTN_WPS		16
 #define WDR4300_GPIO_BTN_RFKILL		17
 
+#define WDR4300_GPIO_EXTERNAL_LNA0	18
+#define WDR4300_GPIO_EXTERNAL_LNA1	19
+
 #define WDR4300_GPIO_USB1_POWER		22
 #define WDR4300_GPIO_USB2_POWER		21
 
@@ -162,6 +165,9 @@ static void __init wdr4300_setup(void)
 					ARRAY_SIZE(wdr4300_gpio_keys),
 					wdr4300_gpio_keys);
 
+	ath79_wmac_set_ext_lna_gpio(0, WDR4300_GPIO_EXTERNAL_LNA0);
+	ath79_wmac_set_ext_lna_gpio(1, WDR4300_GPIO_EXTERNAL_LNA1);
+
 	ath79_init_mac(tmpmac, mac, -1);
 	ath79_register_wmac(art + WDR4300_WMAC_CALDATA_OFFSET, tmpmac);