ximagesrc: send new_segment with GST_FORMAT_TIME format

Instead of using BaseSrc default format GST_FORMAT_BYTES, send it in
GST_FORMAT_TIME.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>

Fixes #611659
diff --git a/sys/ximage/gstximagesrc.c b/sys/ximage/gstximagesrc.c
index 15c7d6c..e6fbe2f 100644
--- a/sys/ximage/gstximagesrc.c
+++ b/sys/ximage/gstximagesrc.c
@@ -1117,6 +1117,7 @@
 static void
 gst_ximage_src_init (GstXImageSrc * ximagesrc, GstXImageSrcClass * klass)
 {
+  gst_base_src_set_format (GST_BASE_SRC (ximagesrc), GST_FORMAT_TIME);
   gst_base_src_set_live (GST_BASE_SRC (ximagesrc), TRUE);
   gst_pad_set_fixatecaps_function (GST_BASE_SRC_PAD (ximagesrc),
       gst_ximage_src_fixate);