gpu:drm:tilcdc: get preferred_bpp value from DT

The preferred_bpp value in currently hard-coded to 16.
This causes color corruption on the am335x-evm lcd panel which
requires 32 bpp instead. This changes attempts to use the configured
bpp value from the DT or built-in panel-info struct.

Signed-off-by: Benoit Parrot <bparrot@ti.com>
Acked-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/tilcdc/tilcdc_panel.c b/drivers/gpu/drm/tilcdc/tilcdc_panel.c
index 0917665..86c6732 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_panel.c
+++ b/drivers/gpu/drm/tilcdc/tilcdc_panel.c
@@ -393,6 +393,8 @@
 		goto fail;
 	}
 
+	mod->preferred_bpp = panel_mod->info->bpp;
+
 	panel_mod->backlight = of_find_backlight_by_node(node);
 	if (panel_mod->backlight)
 		dev_info(&pdev->dev, "found backlight\n");