src/acpi: Add guards on all header files

Change-Id: I1b2d82a85194df6660bc041af8a690acc5469d02
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/20735
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>

src/acpi/sata.h

@@ -11,6 +11,11 @@
  * GNU General Public License for more details.
  */
 
+#ifndef __ACPI_SATA_H__
+#define __ACPI_SATA_H__
+
 #include <stdint.h>
 
 void generate_sata_ssdt_ports(const char *scope, uint32_t enable_map);
+
+#endif