Bluetooth: Restrict access for raw-only controllers

Bluetooth controllers that are marked for raw-only usage can only be
used with user channel access. Any other operation should be rejected.

This simplifies the whole raw-only support since it now depends on
the fact that the controller is marked with HCI_QUIRK_RAW_DEVICE and
runtime raw access is restricted to user channel operation.

The kernel internal processing of HCI commands and events is designed
around the case that either the kernel has full control over the device
or that the device is driven from userspace. This now makes a clear
distinction between these two possible operation modes.

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