ARM: rmobile: Use PRR driver on all Gen3 boards

Mark the PRR as u-boot,dm-pre-reloc in all Gen3 board DTs as it is
needed very early and turn on the CONFIG_SYSCON to allow the PRR
driver to bind as a syscon uclass.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
diff --git a/arch/arm/dts/r8a7796.dtsi b/arch/arm/dts/r8a7796.dtsi
index 9e6a5f2..6a6bfd4 100644
--- a/arch/arm/dts/r8a7796.dtsi
+++ b/arch/arm/dts/r8a7796.dtsi
@@ -377,6 +377,7 @@
 		prr: chipid@fff00044 {
 			compatible = "renesas,prr";
 			reg = <0 0xfff00044 0 4>;
+			u-boot,dm-pre-reloc;
 		};
 
 		sysc: system-controller@e6180000 {