test: dm: Use UTF_CONSOLE in tests

Set this flag rather than doing things manually in the test.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/test/dm/mux-cmd.c b/test/dm/mux-cmd.c
index 3aadc15..6eb3b28 100644
--- a/test/dm/mux-cmd.c
+++ b/test/dm/mux-cmd.c
@@ -109,7 +109,7 @@
 
 	return 0;
 }
-DM_TEST(dm_test_cmd_mux_list, UTF_SCAN_PDATA | UTF_SCAN_FDT);
+DM_TEST(dm_test_cmd_mux_list, UTF_SCAN_PDATA | UTF_SCAN_FDT | UTF_CONSOLE);
 
 static int dm_test_cmd_mux_select(struct unit_test_state *uts)
 {