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_drv.h b/drivers/gpu/drm/tilcdc/tilcdc_drv.h
index 8242b5a..0906843 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_drv.h
+++ b/drivers/gpu/drm/tilcdc/tilcdc_drv.h
@@ -89,6 +89,7 @@
 	const char *name;
 	struct list_head list;
 	const struct tilcdc_module_ops *funcs;
+	unsigned int preferred_bpp;
 };
 
 void tilcdc_module_init(struct tilcdc_module *mod, const char *name,