rockchip: dts: rk3399-firefly: update gmac parameter

Update the tx_delay and rx_delay to match the timing for
rk3399-firefly board to improve the stability of gmac data
transfer.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

arch/arm/dts/rk3399-firefly.dts

@@ -211,8 +211,8 @@
 	snps,reset-gpio = <&gpio3 RK_PB7 GPIO_ACTIVE_LOW>;
 	snps,reset-active-low;
 	snps,reset-delays-us = <0 10000 50000>;
-	tx_delay = <0x28>;
+	tx_delay = <0x33>;
-	rx_delay = <0x11>;
+	rx_delay = <0x45>;
 	status = "okay";
 };