Fix overly specific description in public doc

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/include/mbedtls/md.h b/include/mbedtls/md.h
index f717618..a5a294d 100644
--- a/include/mbedtls/md.h
+++ b/include/mbedtls/md.h
@@ -464,8 +464,8 @@
 const mbedtls_md_info_t *mbedtls_md_info_from_string(const char *md_name);
 
 /**
- * \brief           This function extracts the message-digest name from the
- *                  message-digest information structure.
+ * \brief           This function returns the name of the message digest for
+ *                  the message-digest information structure given.
  *
  * \param md_info   The information structure of the message-digest algorithm
  *                  to use.