Bluetooth: btusb: Use proper data structures for Intel vendor events

The Intel vendors events indicating firmware loading result and the
bootup of the operational firmware are currently hardcoded byte
comparisons. So intead of doing that, provide proper data structures
and actually use them.

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