usb: musb: fix otg default state

Right after the musb_hdrc driver is loaded, the otg default state
is a_idle, and Mode=Host, which are set by musb_host_setup().

This causes the following kernel message during musb gadget
enumeration.

	CAUTION: musb: Babble Interrupt Occurred

This patch sets the otg default state to b_idle, and its Mode to
Peripheral.

It has been validated on TI AM335x GP EVM USB0 port with g_zero.
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/musb/musb_gadget.c

@@ -1790,6 +1790,10 @@ int musb_gadget_setup(struct musb *musb)
 	musb->g.max_speed = USB_SPEED_HIGH;
 	musb->g.speed = USB_SPEED_UNKNOWN;
 
+	MUSB_DEV_MODE(musb);
+	musb->xceiv->otg->default_a = 0;
+	musb->xceiv->state = OTG_STATE_B_IDLE;
+
 	/* this "gadget" abstracts/virtualizes the controller */
 	musb->g.name = musb_driver_name;
 	musb->g.is_otg = 1;