x86/power: Support objtool validation in hibernate_asm_64.S

The OBJECT_FILES_NON_STANDARD annotation is used to tell objtool to
ignore a file.  File-level ignores won't work when validating vmlinux.o.

Instead, convert restore_image() and core_restore_code() to be ELF
functions.  Their code is conventional enough for objtool to be able to
understand them.

Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/974f8ceb5385e470f72e93974c70ab5c894bb0dc.1611263462.git.jpoimboe@redhat.com

arch/x86/power/Makefile

 # SPDX-License-Identifier: GPL-2.0
-OBJECT_FILES_NON_STANDARD_hibernate_asm_$(BITS).o := y
 
 # __restore_processor_state() restores %gs after S3 resume and so should not
 # itself be stack-protected

arch/x86/power/hibernate_asm_64.S

@@ -99,7 +99,7 @@ SYM_FUNC_START(swsusp_arch_suspend)
 	ret
 SYM_FUNC_END(swsusp_arch_suspend)
 
-SYM_CODE_START(restore_image)
+SYM_FUNC_START(restore_image)
 	/* prepare to jump to the image kernel */
 	movq	restore_jump_address(%rip), %r8
 	movq	restore_cr3(%rip), %r9
@@ -115,10 +115,10 @@ SYM_CODE_START(restore_image)
 	movq	relocated_restore_code(%rip), %rcx
 	ANNOTATE_RETPOLINE_SAFE
 	jmpq	*%rcx
-SYM_CODE_END(restore_image)
+SYM_FUNC_END(restore_image)
 
 	/* code below has been relocated to a safe page */
-SYM_CODE_START(core_restore_code)
+SYM_FUNC_START(core_restore_code)
 	/* switch to temporary page tables */
 	movq	%rax, %cr3
 	/* flush TLB */
@@ -147,4 +147,4 @@ SYM_CODE_START(core_restore_code)
 	/* jump to the restore_registers address from the image header */
 	ANNOTATE_RETPOLINE_SAFE
 	jmpq	*%r8
-SYM_CODE_END(core_restore_code)
+SYM_FUNC_END(core_restore_code)