x86: convert compressed loader 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".

Linus suggested that we merge the ".text.head" section with ".text"
(presumably while preserving the fact that the head code starts at 0).
When I tried this it caused the kernel to not boot.
Signed-off-by: NTim Abbott <tabbott@ksplice.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

arch/x86/boot/compressed/head_32.S

@@ -23,13 +23,14 @@
  */
 	.text
 
+#include <linux/init.h>
 #include <linux/linkage.h>
 #include <asm/segment.h>
 #include <asm/page_types.h>
 #include <asm/boot.h>
 #include <asm/asm-offsets.h>
 
-	.section ".text.head","ax",@progbits
+	__HEAD
 ENTRY(startup_32)
 	cld
 	/*

arch/x86/boot/compressed/head_64.S

@@ -24,6 +24,7 @@
 	.code32
 	.text
 
+#include <linux/init.h>
 #include <linux/linkage.h>
 #include <asm/segment.h>
 #include <asm/pgtable_types.h>
@@ -33,7 +34,7 @@
 #include <asm/processor-flags.h>
 #include <asm/asm-offsets.h>
 
-	.section ".text.head"
+	__HEAD
 	.code32
 ENTRY(startup_32)
 	cld

arch/x86/boot/compressed/vmlinux.lds.S

+#include <asm-generic/vmlinux.lds.h>
+
 OUTPUT_FORMAT(CONFIG_OUTPUT_FORMAT, CONFIG_OUTPUT_FORMAT, CONFIG_OUTPUT_FORMAT)
 
 #undef i386
@@ -18,9 +20,9 @@ SECTIONS
 	 * address 0.
 	 */
 	. = 0;
-	.text.head : {
+	.head.text : {
 		_head = . ;
-		*(.text.head)
+		HEAD_TEXT
 		_ehead = . ;
 	}
 	.rodata.compressed : {