Fix writing less than 4K

ddrio.c

@@ -212,7 +212,7 @@ write_to_ddr (pcilib_t *pci, volatile void *bar, Options *opts)
 
     copy_data (bar, data, size, opts);
 
-    if (size % 4096) {
+    if (size >= 4096 && size % 4096) {
         size_t remaining = 4096 - size % 4096;
 
         memset (data, 0, remaining);