usb: gadget: udc: renesas_usb3: Fix b-device mode for "workaround"

If the "workaround_for_vbus" is true, the driver will not call
usb_disconnect(). So, since the controller keeps some registers'
value, the driver doesn't re-enumarate suitable speed after
the b-device mode is disabled. To fix the issue, this patch
adds usb_disconnect() calling in renesas_usb3_b_device_write()
if workaround_for_vbus is true.

Fixes: 43ba968b ("usb: gadget: udc: renesas_usb3: add debugfs to set the b-device mode")
Cc: <stable@vger.kernel.org> # v4.14+
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/gadget/udc/renesas_usb3.c

@@ -2437,6 +2437,9 @@ static ssize_t renesas_usb3_b_device_write(struct file *file,
 	else
 		usb3->forced_b_device = false;
 
+	if (usb3->workaround_for_vbus)
+		usb3_disconnect(usb3);
+
 	/* Let this driver call usb3_connect() anyway */
 	usb3_check_id(usb3);