Un-unrestore mbedtls_x509_string_to_names()

Re-restore mbedtls_x509_string_to_names() to public as our example
programs use it, and it is the reverse of mbedtls_x509_dn_gets().

Add a docstring, so that it is a properly documented public function.

Signed-off-by: David Horstmann <david.horstmann@arm.com>

include/mbedtls/x509.h

@@ -322,6 +322,23 @@ mbedtls_x509_san_list;
  */
 int mbedtls_x509_dn_gets(char *buf, size_t size, const mbedtls_x509_name *dn);
 
+/**
+ * \brief            Convert the certificate DN string \p name into
+ *                   a linked list of mbedtls_x509_name (equivalent to
+ *                   mbedtls_asn1_named_data).
+ *
+ * \note             This function allocates a linked list, and places the head
+ *                   pointer in \p head. This list must later be freed by a
+ *                   call to mbedtls_asn1_free_named_data_list().
+ *
+ * \param[out] head  Address in which to store the pointer to the head of the
+ *                   allocated list of mbedtls_x509_name
+ * \param[in] name   The string representation of a DN to convert
+ *
+ * \return           0 on success, or a negative error code.
+ */
+int mbedtls_x509_string_to_names(mbedtls_asn1_named_data **head, const char *name);
+
 /**
  * \brief          Return the next relative DN in an X509 name.
  *

library/x509_internal.h

@@ -21,7 +21,6 @@
 #include "mbedtls/rsa.h"
 #endif
 
-int mbedtls_x509_string_to_names(mbedtls_asn1_named_data **head, const char *name);
 int mbedtls_x509_get_name(unsigned char **p, const unsigned char *end,
                           mbedtls_x509_name *cur);
 int mbedtls_x509_get_alg_null(unsigned char **p, const unsigned char *end,