OMAPDSS: fix dss_get_ctx_loss_count for DT

When using DT, dss device does not have platform data. However,
dss_get_ctx_loss_count() uses dss device's platform data to find the
get_ctx_loss_count function pointer.

To fix this, dss_get_ctx_loss_count() needs to be changed to get the
platform data from the omapdss device, which is a "virtual" device and
always has platform data.
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

drivers/video/omap2/dss/dss.c

@@ -157,7 +157,8 @@ static void dss_restore_context(void)
 
 int dss_get_ctx_loss_count(void)
 {
-	struct omap_dss_board_info *board_data = dss.pdev->dev.platform_data;
+	struct platform_device *core_pdev = dss_get_core_pdev();
+	struct omap_dss_board_info *board_data = core_pdev->dev.platform_data;
 	int cnt;
 
 	if (!board_data->get_context_loss_count)