usb: Migrate to support live DT for some driver

Use ofnode_ instead of fdt_ APIs so that the drivers can support live DT.
This patch updates usb_get_dr_mode() and usb_get_maximum_speed() to use
ofnode as parameter instead of fdt offset. And all the drivers who use
these APIs update to use live dt APIs at the same time.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/drivers/usb/host/ehci-mx6.c b/drivers/usb/host/ehci-mx6.c
index 1993ad6..f2ceb51 100644
--- a/drivers/usb/host/ehci-mx6.c
+++ b/drivers/usb/host/ehci-mx6.c
@@ -513,7 +513,7 @@
 	struct usb_platdata *plat = dev_get_platdata(dev);
 	enum usb_dr_mode dr_mode;
 
-	dr_mode = usb_get_dr_mode(dev_of_offset(dev));
+	dr_mode = usb_get_dr_mode(dev->node);
 
 	switch (dr_mode) {
 	case USB_DR_MODE_HOST: