x86: Make use of binman expanded entries

We don't need to spell out the separate pieces of U-Boot phase binaries
anymore. Revert to using the simple entry and let binman do the expansion
itself as needed.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/x86/dts/u-boot.dtsi

@@ -38,20 +38,11 @@
 	};
 #endif
 	spl {
-		type = "section";
+		type = "u-boot-spl";
 		offset = <CONFIG_X86_OFFSET_SPL>;
-		u-boot-spl {
-		};
-		u-boot-spl-dtb {
-		};
 	};
 	u-boot {
-		type = "section";
 		offset = <CONFIG_X86_OFFSET_U_BOOT>;
-		u-boot-nodtb {
-		};
-		u-boot-dtb {
-		};
 	};
 #elif defined(CONFIG_SPL)
 	u-boot-spl-with-ucode-ptr {