x86_64: Squash initial_code modpost warnings

Get rid of warnings like

WARNING: vmlinux.o(.bootstrap.text+0x1a8): Section mismatch: reference to .init.text:x86_64_start_kernel (between 'initial_code' and 'init_rsp')

- Move initialization code into .text.head like i386 because modpost knows about this already
- Mark initial_code .initdata
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86_64/kernel/head.S

@@ -25,7 +25,7 @@
  */
 
 	.text
-	.section .bootstrap.text
+	.section .text.head
 	.code64
 	.globl startup_64
 startup_64:
@@ -243,10 +243,16 @@ ENTRY(secondary_startup_64)
 	lretq
 
 	/* SMP bootup changes these two */
+#ifndef CONFIG_HOTPLUG_CPU
+	.pushsection .init.data
+#endif
 	.align	8
 	.globl	initial_code
 initial_code:
 	.quad	x86_64_start_kernel
+#ifndef CONFIG_HOTPLUG_CPU
+	.popsection
+#endif
 	.globl init_rsp
 init_rsp:
 	.quad  init_thread_union+THREAD_SIZE-8

arch/x86_64/kernel/vmlinux.lds.S

@@ -28,7 +28,7 @@ SECTIONS
   _text = .;			/* Text and read-only data */
   .text :  AT(ADDR(.text) - LOAD_OFFSET) {
 	/* First the code that has to be first for bootstrapping */
-	*(.bootstrap.text)
+	*(.text.head)
 	_stext = .;
 	/* Then the rest */
 	TEXT_TEXT