USB: dbgp gadget: set MaxpacketSize0

The current code doesn't set it, so linux complains about
it when connected, and ignores the device:

[104611.068082] usb 1-5: new high speed USB device using ehci_hcd and address 127
[104611.088368] usb 1-5: Invalid ep0 maxpacket: 0
Signed-off-by: Sven Schnelle <svens@stackframe.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/gadget/dbgp.c

@@ -312,6 +312,7 @@ static int __init dbgp_bind(struct usb_gadget *gadget)
 
 	dbgp.req->length = DBGP_REQ_EP0_LEN;
 	gadget->ep0->driver_data = gadget;
+	device_desc.bMaxPacketSize0 = gadget->ep0->maxpacket;
 
 #ifdef CONFIG_USB_G_DBGP_SERIAL
 	dbgp.serial = kzalloc(sizeof(struct gserial), GFP_KERNEL);