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/cpu/u-boot.lds b/arch/x86/cpu/u-boot.lds
index 2313cd7..8e185f3 100644
--- a/arch/x86/cpu/u-boot.lds
+++ b/arch/x86/cpu/u-boot.lds
@@ -67,6 +67,8 @@
 	__rel_dyn_start = .;
 	.rel.dyn : { *(.rel.dyn) }
 	__rel_dyn_end = .;
+	. = ALIGN(4);
+	_end = .;
 
 	/DISCARD/ : { *(.dynstr*) }
 	/DISCARD/ : { *(.dynamic*) }