rockchip: generate idbloader.img content for u-boot-rockchip.bin with binman for ARM

idbloader.img content - currently created by way of Makefile - can be
created by binman directly.

So let's do that for Rockchip ARM platforms.

Cc: Quentin Schulz <foss+uboot@0leil.net>
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/arch/arm/dts/rockchip-u-boot.dtsi b/arch/arm/dts/rockchip-u-boot.dtsi
index eae3ee7..ad72ca9 100644
--- a/arch/arm/dts/rockchip-u-boot.dtsi
+++ b/arch/arm/dts/rockchip-u-boot.dtsi
@@ -17,8 +17,17 @@
 		filename = "u-boot-rockchip.bin";
 		pad-byte = <0xff>;
 
-		blob {
+		mkimage {
 			filename = "idbloader.img";
+			args = "-n", CONFIG_SYS_SOC, "-T", "rksd";
+#ifdef CONFIG_TPL
+			multiple-data-files;
+
+			u-boot-tpl {
+			};
+#endif
+			u-boot-spl {
+			};
 		};
 
 		u-boot-img {