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/southbridge/amd/agesa/hudson/spi.c

@@ -14,7 +14,6 @@
  */
 #include <stdint.h>
 #include <stdlib.h>
-#include <string.h>
 #include <device/mmio.h>
 #include <console/console.h>
 #include <spi_flash.h>

src/southbridge/amd/amd8111/lpc.c

@@ -29,7 +29,7 @@
 #include <cpu/amd/powernow.h>
 #endif
 #include <stdlib.h>
-#include <string.h>
+
 #include "amd8111.h"
 
 #define NMI_OFF 0

src/southbridge/amd/cimx/sb800/spi.c

@@ -14,7 +14,6 @@
  */
 #include <stdint.h>
 #include <stdlib.h>
-#include <string.h>
 #include <device/mmio.h>
 #include <console/console.h>
 #include <spi_flash.h>

src/southbridge/amd/common/amd_pci_util.c

@@ -17,7 +17,6 @@
 #include <device/pci.h>
 #include <arch/io.h>
 #include <device/pci_ops.h>
-#include <string.h>
 #include "amd_pci_util.h"
 #include <pc80/i8259.h>
 #include "amd_pci_int_defs.h"

src/southbridge/amd/sb700/spi.c

@@ -16,7 +16,6 @@
 
 #include <stdint.h>
 #include <stdlib.h>
-#include <string.h>
 #include <device/mmio.h>
 #include <console/console.h>
 #include <spi-generic.h>