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>
diff --git a/src/soc/intel/baytrail/southcluster.c b/src/soc/intel/baytrail/southcluster.c
index 7b01cfa..0289e8b 100644
--- a/src/soc/intel/baytrail/southcluster.c
+++ b/src/soc/intel/baytrail/southcluster.c
@@ -30,6 +30,7 @@
 #include <device/pci_ids.h>
 #include <pc80/mc146818rtc.h>
 #include <drivers/uart/uart8250reg.h>
+#include <string.h>
 
 #include <soc/iomap.h>
 #include <soc/irq.h>