ARM: dts: am335x-sl50: set dr_mode to otg

The board can be either a host, or a peripheral, so set the controller as
OTG mode to reflect this.
Signed-off-by: NEnric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: NTony Lindgren <tony@atomide.com>

arch/arm/boot/dts/am335x-sl50.dts

@@ -476,7 +476,7 @@
 
 &usb0 {
 	status = "okay";
-	dr_mode = "peripheral";
+	dr_mode = "otg";
 };
 
 &usb1 {