arm64: dts: ls208xa: specify clock frequencies for the MDIO controllers

Up until now, the external MDIO controller frequency values relied
either on the default ones out of reset or on those setup by u-boot.
Let's just properly specify the MDC frequency in the DTS so that even
without u-boot's intervention Linux can drive the MDIO bus.

Fixes: 0420dde3 ("arm64: dts: ls208xa: add the external MDIO nodes")
Signed-off-by: NIoana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/fsl-ls208xa.dtsi

@@ -532,6 +532,9 @@
 			little-endian;
 			#address-cells = <1>;
 			#size-cells = <0>;
+			clock-frequency = <2500000>;
+			clocks = <&clockgen QORIQ_CLK_PLATFORM_PLL
+					    QORIQ_CLK_PLL_DIV(2)>;
 			status = "disabled";
 		};
 
@@ -541,6 +544,9 @@
 			little-endian;
 			#address-cells = <1>;
 			#size-cells = <0>;
+			clock-frequency = <2500000>;
+			clocks = <&clockgen QORIQ_CLK_PLATFORM_PLL
+					    QORIQ_CLK_PLL_DIV(2)>;
 			status = "disabled";
 		};