monitor: convert do_memory_save() to QError

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

monitor.c

diff --git a/monitor.c b/monitor.c
index 0595f0d..7b7a465 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1316,7 +1316,7 @@
 
     f = fopen(filename, "wb");
     if (!f) {
-        monitor_printf(mon, "could not open '%s'\n", filename);
+        qemu_error_new(QERR_OPEN_FILE_FAILED, filename);
         return;
     }
     while (size != 0) {