drm/omap: dispc: disp_wb_setup to check return code

When dispc_wb_setup() calls dispc_ovl_setup_common() it does not
check for failure but instead keeps on partially setting up WB.
This causes the WB H/W to be partially initialized and yield
unexpected behavior.

Make sure return code is successful before proceeding.
Signed-off-by: Benoit Parrot <bparrot@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

drivers/gpu/drm/omapdrm/dss/dispc.c

@@ -2783,6 +2783,8 @@ int dispc_wb_setup(struct dispc_device *dispc,
 		wi->height, wi->fourcc, wi->rotation, zorder,
 		wi->pre_mult_alpha, global_alpha, wi->rotation_type,
 		replication, vm, mem_to_mem);
+	if (r)
+		return r;
 
 	switch (wi->fourcc) {
 	case DRM_FORMAT_RGB565:
@@ -2823,7 +2825,7 @@ int dispc_wb_setup(struct dispc_device *dispc,
 		REG_FLD_MOD(dispc, DISPC_OVL_ATTRIBUTES2(plane), wbdelay, 7, 0);
 	}
 
-	return r;
+	return 0;
 }
 
 static int dispc_ovl_enable(struct dispc_device *dispc,