powerpc: convert to use __HEAD and HEAD_TEXT macros.

This has the consequence of changing the section name use for head
code from ".text.head" to ".head.text".  Since this commit changes all
users in the architecture, this change should be harmless.

Signed-off-by: Tim Abbott <tabbott@mit.edu>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/powerpc/kernel/head_40x.S

@@ -31,6 +31,7 @@
  *
  */
 
+#include <linux/init.h>
 #include <asm/processor.h>
 #include <asm/page.h>
 #include <asm/mmu.h>
@@ -52,7 +53,7 @@
  *
  * This is all going to change RSN when we add bi_recs.......  -- Dan
  */
-	.section	.text.head, "ax"
+	__HEAD
 _ENTRY(_stext);
 _ENTRY(_start);