usb-mtp: fix usb_mtp_get_device_info so that libmtp on the guest doesn't complain

usb-mtp: fix usb_mtp_get_device_info so that libmtp on the guest doesn't complain

If an application uses libmtp on the guest system,
it will complain with the warning message:
LIBMTP WARNING: VendorExtensionID: ffffffff
LIBMTP WARNING: VendorExtensionDesc: (null)
LIBMTP WARNING: this typically means the device is PTP (i.e. a camera) but
not a MTP device at all. Trying to continue anyway.

This is because libmtp expects a MTP Vendor Extension ID of 0x00000006 and a
MTP Version of 0x0064. These numbers are taken from Microsoft's MTP Vendor
Extension Identification Message page and are what most physical devices
show.

Signed-off-by: Isaac Lozano <109lozanoi@gmail.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1460892593-5908-1-git-send-email-109lozanoi@gmail.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>