usb: of: add an api to get dr_mode by the phy node

Some USB phy drivers have different handling for the controller in each
dr_mode. But the phy driver does not have visibility to the dr_mode of
the controller.

This adds an api to return the dr_mode of the controller which
associates the given phy node.

Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/include/linux/usb/of.h b/include/linux/usb/of.h
index c3fe9e4..3805757 100644
--- a/include/linux/usb/of.h
+++ b/include/linux/usb/of.h
@@ -12,10 +12,15 @@
 #include <linux/usb/phy.h>
 
 #if IS_ENABLED(CONFIG_OF)
+enum usb_dr_mode of_usb_get_dr_mode_by_phy(struct device_node *phy_np);
 bool of_usb_host_tpl_support(struct device_node *np);
 int of_usb_update_otg_caps(struct device_node *np,
 			struct usb_otg_caps *otg_caps);
 #else
+enum usb_dr_mode of_usb_get_dr_mode_by_phy(struct device_node *phy_np)
+{
+	return USB_DR_MODE_UNKNOWN;
+}
 static inline bool of_usb_host_tpl_support(struct device_node *np)
 {
 	return false;