ar71xx: fix reset key for TP-Link TL-WR802N V1/V2

During porting support for this router to ath79 target
it was discovered that GPIO mapping was incorrect (GPIO11 active high).
Correct mapping for both V1 and V2 is GPIO12 active low.

Default configuration from GPL source for V2 explicitly states this, and
this was confirmed experimentally on ath79 by looking on
/sys/kernel/debug/gpio. Correctness of this was also validated for V1 by
cross-flashing vendor firmware for V1 on V2 hardware, in which reset
button also worked.

Fix it.

Signed-off-by: Lech Perczak <lech.perczak@gmail.com>
[slightly adjust commit title]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
(cherry picked from commit f841e706403b1a111cbb6dc5930b7886307bf633)

target/linux/ar71xx/files/arch/mips/ath79/mach-tl-wr802n.c

@@ -24,7 +24,7 @@
 #include "machtypes.h"
 
 #define TL_WR802N_GPIO_LED_SYSTEM	13
-#define TL_WR802N_GPIO_BTN_RESET	11
+#define TL_WR802N_GPIO_BTN_RESET	12
 
 #define TL_WR802N_KEYS_POLL_INTERVAL		20 /* msecs */
 #define TL_WR802N_KEYS_DEBOUNCE_INTERVAL	(3 * TL_WR802N_KEYS_POLL_INTERVAL)
@@ -61,7 +61,7 @@ static struct gpio_keys_button tl_wr802n_gpio_keys[] __initdata = {
 		.code		= KEY_RESTART,
 		.debounce_interval = TL_WR802N_KEYS_DEBOUNCE_INTERVAL,
 		.gpio		= TL_WR802N_GPIO_BTN_RESET,
-		.active_low	= 0,
+		.active_low	= 1,
 	}
 };