src: Use 'include <string.h>' when appropriate

Drop 'include <string.h>' when it is not used and
add it when it is missing.
Also extra lines removed, or added just before local includes.

Change-Id: Iccac4dbaa2dd4144fc347af36ecfc9747da3de20
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/31966
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

src/mainboard/google/slippy/acpi_tables.c

@@ -14,16 +14,15 @@
  */
 
 #include <types.h>
-#include <string.h>
 #include <arch/acpi.h>
 #include <arch/smp/mpspec.h>
 #include <device/device.h>
 #include <device/pci.h>
 #include <vendorcode/google/chromeos/gnvs.h>
 #include <ec/google/chromeec/ec.h>
-
 #include <southbridge/intel/lynxpoint/pch.h>
 #include <southbridge/intel/lynxpoint/nvs.h>
+
 #include "thermal.h"
 
 static void acpi_update_thermal_table(global_nvs_t *gnvs)