xen-disk: use g_new0 to fix build

g_malloc0_n is available since glib-2.24. To allow build with older glib
versions use the generic g_new0, which is already used in many other
places in the code.

Fixes commit 3284fad7 ("xen-disk: add support for multi-page shared rings")
Signed-off-by: NOlaf Hering <olaf@aepfle.de>
Reviewed-by: NStefano Stabellini <sstabellini@kernel.org>
Signed-off-by: NStefano Stabellini <sstabellini@kernel.org>

hw/block/xen_disk.c

@@ -1232,7 +1232,7 @@ static int blk_connect(struct XenDevice *xendev)
         return -1;
     }
 
-    domids = g_malloc0_n(blkdev->nr_ring_ref, sizeof(uint32_t));
+    domids = g_new0(uint32_t, blkdev->nr_ring_ref);
     for (i = 0; i < blkdev->nr_ring_ref; i++) {
         domids[i] = blkdev->xendev.dom;
     }