drm/msm/dp: Make it possible to enable the test pattern

The debugfs interface contains the knobs to make the DisplayPort
controller output a test pattern, unfortunately there's nothing
currently that actually enables the defined test pattern.

Fixes: de3ee25 ("drm/msm/dp: add debugfs nodes for video pattern tests")
Link: https://lore.kernel.org/linux-arm-msm/20210629002234.1787149-1-bjorn.andersson@linaro.org/
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/gpu/drm/msm/dp/dp_debug.c

@@ -165,6 +165,8 @@ static ssize_t dp_test_active_write(struct file *file,
 			debug->panel->video_test = true;
 		else
 			debug->panel->video_test = false;
+
+		dp_panel_tpg_config(debug->panel, debug->panel->video_test);
 	}
 	kfree(input_buffer);