libc: Fix all includes in codebase

The codebase was using non-standard headers. It is needed to replace
them by the correct ones so that we can use the new libc headers.

Change-Id: I530f71d9510cb036e69fe79823c8230afe890b9d
Acked-by: Sumit Garg <sumit.garg@linaro.org>
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/plat/hisilicon/hikey/hikey_security.c b/plat/hisilicon/hikey/hikey_security.c
index 863ad2b..43d7b7a 100644
--- a/plat/hisilicon/hikey/hikey_security.c
+++ b/plat/hisilicon/hikey/hikey_security.c
@@ -8,7 +8,7 @@
 #include <debug.h>
 #include <platform_def.h>
 #include <stdint.h>
-#include <strings.h>
+#include <string.h>
 #include <utils_def.h>
 #include "hikey_private.h"