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/commonlib/storage/pci_sdhci.c

@@ -22,8 +22,10 @@
 #include <commonlib/sdhci.h>
 #include <device/pci.h>
 #include <device/pci_ops.h>
-#include "sd_mmc.h"
 #include <stdint.h>
+#include <string.h>
+
+#include "sd_mmc.h"
 #include "storage.h"
 
 /* Initialize an SDHCI port */