x86: acpi: Add wake up assembly stub

This adds a wake up stub before jumping to OS wake up vector.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Stefan Roese <sr@denx.de>
diff --git a/arch/x86/include/asm/acpi_s3.h b/arch/x86/include/asm/acpi_s3.h
index 10cedde..a06466c 100644
--- a/arch/x86/include/asm/acpi_s3.h
+++ b/arch/x86/include/asm/acpi_s3.h
@@ -7,6 +7,8 @@
 #ifndef __ASM_ACPI_S3_H__
 #define __ASM_ACPI_S3_H__
 
+#define WAKEUP_BASE	0x600
+
 /* PM1_STATUS register */
 #define WAK_STS		(1 << 15)
 #define PCIEXPWAK_STS	(1 << 14)
@@ -27,6 +29,11 @@
 #define SLP_TYP_S4	6
 #define SLP_TYP_S5	7
 
+#ifndef __ASSEMBLY__
+
+extern char __wakeup[];
+extern int __wakeup_size;
+
 enum acpi_sleep_state {
 	ACPI_S0,
 	ACPI_S1,
@@ -92,4 +99,6 @@
  */
 void chipset_clear_sleep_state(void);
 
+#endif /* __ASSEMBLY__ */
+
 #endif /* __ASM_ACPI_S3_H__ */