ChromeOS: Add missing prototype for acpi_get_vdat_info()

Change-Id: I4bd9b52cfc24a8ff73be05ee535b9e16c0d9bd79
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Reviewed-on: http://review.coreboot.org/946
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
Tested-by: build bot (Jenkins)

src/arch/x86/include/arch/acpi.h

@@ -498,4 +498,8 @@ void generate_cpu_entries(void);
 
 #endif	/* CONFIG_GENERATE_ACPI_TABLES */
 
+#if CONFIG_CHROMEOS
+void acpi_get_vdat_info(void **vdat_addr, uint32_t *vdat_size);
+#endif /* CONFIG_CHROMEOS */
+
 #endif  /* __ASM_ACPI_H */