phy: rcar-gen3-usb2: check dr_mode for otg mode

The previous code assumed a channel has otg capability if a channel
has interrupt property. But, it is not good because:
 - Battery charging feature also needs interrupt property.
 - Some R-Car Gen3 SoCs (e.g. R-Car D3) don't have OTG capability.

So, this patch checks whether usb 2.0 host node has dr_mode property or
not. If it has 'dr_mode = "otg";', this driver enables otg capability.
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>

drivers/phy/renesas/phy-rcar-gen3-usb2.c

 /*
  * Renesas R-Car Gen3 for USB2.0 PHY driver
  *
- * Copyright (C) 2015 Renesas Electronics Corporation
+ * Copyright (C) 2015-2017 Renesas Electronics Corporation
  *
  * This is based on the phy-rcar-gen2 driver:
  * Copyright (C) 2014 Renesas Solutions Corp.
@@ -22,6 +22,7 @@
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
 #include <linux/regulator/consumer.h>
+#include <linux/usb/of.h>
 #include <linux/workqueue.h>
 
 /******* USB2.0 Host registers (original offset is +0x200) *******/
@@ -415,13 +416,16 @@ static int rcar_gen3_phy_usb2_probe(struct platform_device *pdev)
 	/* call request_irq for OTG */
 	irq = platform_get_irq(pdev, 0);
 	if (irq >= 0) {
-		int ret;
-
 		INIT_WORK(&channel->work, rcar_gen3_phy_usb2_work);
 		irq = devm_request_irq(dev, irq, rcar_gen3_phy_usb2_irq,
 				       IRQF_SHARED, dev_name(dev), channel);
 		if (irq < 0)
 			dev_err(dev, "No irq handler (%d)\n", irq);
+	}
+
+	if (of_usb_get_dr_mode_by_phy(dev->of_node, 0) == USB_DR_MODE_OTG) {
+		int ret;
+
 		channel->has_otg = true;
 		channel->extcon = devm_extcon_dev_allocate(dev,
 							rcar_gen3_phy_cable);