[opensbi] create opensbi from T-Head official:

repo: https://github.com/T-head-Semi/opensbi
	commit: 89182b257c8798e15e4c685c1af0c2862d528d2a

Change-Id: I7b39d66729e0108661a6f4c9e28acbdb303684ea

opensbi/include/sbi/sbi_string.h

@@ -0,0 +1,46 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2019 Western Digital Corporation or its affiliates.
+ *
+ * Authors:
+ *   Atish Patra <atish.patra@wdc.com>
+ */
+
+#ifndef __STRING_H__
+#define __STRING_H__
+
+#include <sbi/sbi_types.h>
+
+/*
+  Provides sbi_strcmp for the completeness of supporting string functions.
+  it is not recommended to use sbi_strcmp() but use sbi_strncmp instead.
+*/
+
+int sbi_strcmp(const char *a, const char *b);
+
+int sbi_strncmp(const char *a, const char *b, size_t count);
+
+size_t sbi_strlen(const char *str);
+
+size_t sbi_strnlen(const char *str, size_t count);
+
+char *sbi_strcpy(char *dest, const char *src);
+
+char *sbi_strncpy(char *dest, const char *src, size_t count);
+
+char *sbi_strchr(const char *s, int c);
+
+char *sbi_strrchr(const char *s, int c);
+
+void *sbi_memset(void *s, int c, size_t count);
+
+void *sbi_memcpy(void *dest, const void *src, size_t count);
+
+void *sbi_memmove(void *dest, const void *src, size_t count);
+
+int sbi_memcmp(const void *s1, const void *s2, size_t count);
+
+void *sbi_memchr(const void *s, int c, size_t count);
+
+#endif