Bluetooth: Add support creating virtual AMP controllers

So far the only option to create a virtual AMP controller was by
setting a module parameter for the hci_vhci driver. This patch adds
the functionality to define inline to create either a BR/EDR or an
AMP controller.

In addition the client will be informed which HCI controller index
it got assigned. That is especially useful for automated end-to-end
testing.

To keep backwards compatibility with existing userspace, the command
for creating a controller type needs to be send right after opening
the device node. If the command is not send, it defaults back to
automatically creating a BR/EDR controller.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>