gpu: ipu-v3: Add ipu_get_num()

Adds of-alias id to ipu_soc and retrieve with ipu_get_num().

Signed-off-by: Steve Longerbeam <steve_longerbeam@mentor.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
diff --git a/drivers/gpu/ipu-v3/ipu-prv.h b/drivers/gpu/ipu-v3/ipu-prv.h
index bfb1e8a..fd47f8f 100644
--- a/drivers/gpu/ipu-v3/ipu-prv.h
+++ b/drivers/gpu/ipu-v3/ipu-prv.h
@@ -152,6 +152,7 @@
 	void __iomem		*cm_reg;
 	void __iomem		*idmac_reg;
 
+	int			id;
 	int			usecount;
 
 	struct clk		*clk;