libc: Import from TF-A

Based on arm-trusted-firware commit 873e394b3bf93214a441f9f98237b58fbbea55aa

Change-Id: I510e092f2b9ff333e9461bdde8d80ed1fab1460c
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>
diff --git a/include/lib/libc/string.h b/include/lib/libc/string.h
new file mode 100644
index 0000000..ee6eeac
--- /dev/null
+++ b/include/lib/libc/string.h
@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2012-2017 Roberto E. Vargas Caballero
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+/*
+ * Portions copyright (c) 2018, ARM Limited and Contributors.
+ * All rights reserved.
+ */
+
+#ifndef STRING_H
+#define STRING_H
+
+#include <string_.h>
+
+#ifndef NULL
+#define NULL ((void *) 0)
+#endif
+
+void *memcpy(void *dst, const void *src, size_t len);
+void *memmove(void *dst, const void *src, size_t len);
+int memcmp(const void *s1, const void *s2, size_t len);
+int strcmp(const char *s1, const char *s2);
+int strncmp(const char *s1, const char *s2, size_t n);
+void *memchr(const void *src, int c, size_t len);
+char *strchr(const char *s, int c);
+void *memset(void *dst, int val, size_t count);
+size_t strlen(const char *s);
+size_t strnlen(const char *s, size_t maxlen);
+char *strrchr(const char *p, int ch);
+size_t strlcpy(char * dst, const char * src, size_t dsize);
+
+#endif /* STRING_H */