Bluetooth: Support HCI_QUIRK_RAW_DEVICE for hci_vhci driver

This adds support for configuring the hci_vhci virtual controllers
as a raw-only device using HCI_QUIRK_RAW_DEVICE. This is useful for
testing the kernel internal infrastructure.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>