db820c: set clk node to be probed before relocation

The clock and serial nodes are needed before relocation.
This patch ensures that the msm-serial driver will probe
and provide uart output before relocation.

Signed-off-by: Ramon Fried <ramon.fried@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

arch/arm/dts/dragonboard820c-uboot.dtsi

@@ -5,6 +5,20 @@
  * (C) Copyright 2017 Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
  */
 
+/ {
+	soc {
+		u-boot,dm-pre-reloc;
+
+		clock-controller@300000 {
+			u-boot,dm-pre-reloc;
+		};
+
+		serial@75b0000 {
+			u-boot,dm-pre-reloc;
+			};
+		};
+};
+
 &pm8994_pon {
 	key_vol_down {
 		gpios = <&pm8994_pon 1 0>;