x86: Add an __end symbol to signal the end of the U-Boot binary

With this symbol we can easy append something (e.g. an FDT) to the U-Boot
binary and access it from within U-Boot.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/lib/init_helpers.c b/arch/x86/lib/init_helpers.c
index 1a097f1..ff2d21f 100644
--- a/arch/x86/lib/init_helpers.c
+++ b/arch/x86/lib/init_helpers.c
@@ -188,7 +188,7 @@
 	gd->fdt_blob = _binary_dt_dtb_start;
 #elif defined CONFIG_OF_SEPARATE
 	/* FDT is at end of image */
-	gd->fdt_blob = (void *)(_end_ofs + _TEXT_BASE);
+	gd->fdt_blob = (ulong *)&_end;
 #endif
 	/* Allow the early environment to override the fdt address */
 	gd->fdt_blob = (void *)getenv_ulong("fdtcontroladdr", 16,