Make two format strings literal

Fixes clang warning
diff --git a/library/x509parse.c b/library/x509parse.c
index bbaca8e..a762855 100644
--- a/library/x509parse.c
+++ b/library/x509parse.c
@@ -3166,7 +3166,7 @@
     if( ret != 0 )
         ret = snprintf( p, n, "???"  );
     else
-        ret = snprintf( p, n, desc );
+        ret = snprintf( p, n, "%s", desc );
     SAFE_SNPRINTF();
 
     if( ( ret = x509_key_size_helper( key_size_str, BEFORE_COLON,
@@ -3274,7 +3274,7 @@
     if( ret != 0 )
         ret = snprintf( p, n, "???"  );
     else
-        ret = snprintf( p, n, desc );
+        ret = snprintf( p, n, "%s", desc );
     SAFE_SNPRINTF();
 
     ret = snprintf( p, n, "\n" );