arm64: dts: rk3399-puma: fix gpio levels for gmac reset pin

The gmac reset has opposite values for the gpio declaration
and the separate reset-active, bring this in line to make
u-boot also find the ethernet-phy.

This mimics the upstream Linux commit found on
https://lore.kernel.org/r/20200603132836.362519-1-heiko@sntech.deSigned-off-by: NHeiko Stuebner <heiko.stuebner@theobroma-systems.com>
Reviewed-by: NPhilipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: NKever Yang <kever.yang@rock-chips.com>

arch/arm/dts/rk3399-puma.dtsi

@@ -157,7 +157,7 @@
 	phy-mode = "rgmii";
 	pinctrl-names = "default";
 	pinctrl-0 = <&rgmii_pins>;
-	snps,reset-gpio = <&gpio3 RK_PC0 GPIO_ACTIVE_HIGH>;
+	snps,reset-gpio = <&gpio3 RK_PC0 GPIO_ACTIVE_LOW>;
 	snps,reset-active-low;
 	snps,reset-delays-us = <0 10000 50000>;
 	tx_delay = <0x10>;