riscv: dts: binman.dtsi: Switch to u-boot-nodtb entry for proper U-Boot

Switch to u-boot-nodtb entry which precisely represents a proper U-Boot
and could be matched with u_boot_any. This allows RISC-V ports that make
use of binman to be built without disabling SPL_BINMAN_UBOOT_SYMBOLS
explicitly, which is set to y by default.

Fixes: 0784510f741 ("riscv: sifive: unleashed: Switch to use binman to generate u-boot.itb")
Suggested-by: Jonas Karlman <jonas@kwiboo.se>
Signed-off-by: Yao Zi <ziyao@disroot.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/riscv/dts/binman.dtsi b/arch/riscv/dts/binman.dtsi
index ceb916b..5aeeedd 100644
--- a/arch/riscv/dts/binman.dtsi
+++ b/arch/riscv/dts/binman.dtsi
@@ -35,7 +35,7 @@
 					compression = "none";
 					load = /bits/ 64 <CONFIG_TEXT_BASE>;
 
-					uboot_blob: blob-ext {
+					uboot_blob: u-boot-nodtb {
 						filename = "u-boot-nodtb.bin";
 					};
 				};