powerpc: ppc4xx: Allow the end of u-boot.bin to be found

Define an _end symbol indicating the end of u-boot.bin. Also add some dummy
words into the link script to ensure that u-boot.bin will always extend
that far. There may be a better way of doing this.

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

arch/powerpc/cpu/ppc4xx/u-boot.lds

@@ -76,9 +76,13 @@ SECTIONS
   . = ALIGN(256);
   __init_begin = .;
   .text.init : { *(.text.init) }
-  .data.init : { *(.data.init) }
-  . = ALIGN(256);
+  .data.init : {
+	*(.data.init)
+	. = ALIGN(256);
+	LONG(0) LONG(0)		/* Extend u-boot.bin to here */
+  }
   __init_end = .;
+  _end = .;
 
 #ifndef CONFIG_SPL
 #ifdef CONFIG_440