usb: common: of_usb_get_maximum_speed to usb_get_maximum_speed

By using the unified device property interface, the function
can be made available for all platforms and not just the
ones using DT.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index cfbcebe..61a5635 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -870,8 +870,9 @@
 	 */
 	hird_threshold = 12;
 
+	dwc->maximum_speed = usb_get_maximum_speed(dev);
+
 	if (node) {
-		dwc->maximum_speed = of_usb_get_maximum_speed(node);
 		dwc->has_lpm_erratum = of_property_read_bool(node,
 				"snps,has-lpm-erratum");
 		of_property_read_u8(node, "snps,lpm-nyet-threshold",