ath79: fix USB power on TP-Link TL-WR810N v1

Before: Kernel reported "usb_vbus: disabling" and the USB was not
        providing power
After:  USB power is switched on, peripheral is powered from the
        device

Signed-off-by: Tom Stöveken <tom@naaa.de>
[squash and tidy up]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
(cherry picked from commit a6f7268dc7)

target/linux/ath79/dts/qca9531_tplink_tl-wr810n-v1.dts

@@ -13,6 +13,7 @@
 		regulator-max-microvolt = <5000000>;
 		gpio = <&gpio 11 GPIO_ACTIVE_HIGH>;
 		enable-active-high;
+		regulator-always-on;
 	};
 };