virtio_bt: Fix alignment in configuration struct

The current version of the configuration structure has unaligned
16-bit fields, but according to the specification [1], access to
the configuration space must be aligned.

Add a second, aligned  version of the configuration structure
and a new feature bit indicating that this version is being used.

[1] https://docs.oasis-open.org/virtio/virtio/v1.1/virtio-v1.1.pdf

Signed-off-by: Igor Skalkin <Igor.Skalkin@opensynergy.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>