rockchip: generate u-boot-rockchip.bin with binman for ARM64 boards

This allows to build u-boot-rockchip.bin binary with binman for Rockchip
ARM64 boards instead of the legacy Makefile way.

Cc: Quentin Schulz <foss+uboot@0leil.net>
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/dts/rockchip-u-boot.dtsi b/arch/arm/dts/rockchip-u-boot.dtsi
index ad72ca9..f90a8bf 100644
--- a/arch/arm/dts/rockchip-u-boot.dtsi
+++ b/arch/arm/dts/rockchip-u-boot.dtsi
@@ -30,7 +30,12 @@
 			};
 		};
 
+#ifdef CONFIG_ARM64
+		blob {
+			filename = "u-boot.itb";
+#else
 		u-boot-img {
+#endif
 			offset = <CONFIG_SPL_PAD_TO>;
 		};
 	};