ARM64: zynqmp: Add u-boot,dm-pre-reloc to clk nodes

Serial driver is getting clk information via DT that's why
also clk node needs to have this flag.

Different behavior was introduced by:
"dm: Use dm_scan_fdt_dev() directly where possible"
(sha1: 91195485)
where simple-bus driver starts to call dm_scan_fdt_dev() which has
additional logic around pre_reloc_only parameter which exclude
clk nodes.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

arch/arm/dts/zynqmp-clk.dtsi

@@ -13,6 +13,7 @@
 		compatible = "fixed-clock";
 		#clock-cells = <0>;
 		clock-frequency = <100000000>;
+		u-boot,dm-pre-reloc;
 	};
 
 	clk125: clk125 {

arch/arm/dts/zynqmp-ep108-clk.dtsi

@@ -13,6 +13,7 @@
 		compatible = "fixed-clock";
 		#clock-cells = <0>;
 		clock-frequency = <25000000>;
+		u-boot,dm-pre-reloc;
 	};
 
 	i2c_clk: i2c_clk {