arm64: dts: ls1088a: 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: bbe75af7 ("arm64: dts: ls1088a: add external MDIO device nodes")
Signed-off-by: NIoana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/fsl-ls1088a.dtsi

@@ -779,6 +779,9 @@
 			little-endian;
 			#address-cells = <1>;
 			#size-cells = <0>;
+			clock-frequency = <2500000>;
+			clocks = <&clockgen QORIQ_CLK_PLATFORM_PLL
+					    QORIQ_CLK_PLL_DIV(1)>;
 			status = "disabled";
 		};
 
@@ -788,6 +791,9 @@
 			little-endian;
 			#address-cells = <1>;
 			#size-cells = <0>;
+			clock-frequency = <2500000>;
+			clocks = <&clockgen QORIQ_CLK_PLATFORM_PLL
+					    QORIQ_CLK_PLL_DIV(1)>;
 			status = "disabled";
 		};