ath79: correctly define WiFi switch for TL-WR841ND v8

The TL-WR841ND v8 feature a WiFi switch instead of a button.
This adds the corresponding input-type to prevent booting into
failsafe regularly.

This has been defined correctly in ar71xx, but was overlooked
when migrating to ath79. In contrast, the TL-WR842ND v2, which
has the key set up as switch in ar71xx, actually has a button.
The TL-MR3420 v2 has a button as well and is set up correctly
for both targets. (Information based on TP-Link user guide)

Note:

While looking into this, I found that support PR for TL-MR3420 v2
switched reset button to ACTIVE_HIGH. However, the other two
device still use ACTIVE_LOW. This seems strange, but I cannot
verify it lacking the affected devices.

Fixes: FS#2733
Fixes: 9601d94138 ("add support for TP-Link TL-WR841N/ND v8")

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
(backported from commit 5e86877f36)

target/linux/ath79/dts/ar9341_tplink_tl-wr841-v8.dts

@@ -32,6 +32,7 @@
 		rfkill {
 			label = "WiFi";
 			linux,code = <KEY_RFKILL>;
+			linux,input-type = <EV_SW>;
 			gpios = <&gpio 16 GPIO_ACTIVE_HIGH>;
 			debounce-interval = <60>;
 		};