Bluetooth: Add basic IRK management support

This patch adds the initial IRK storage and management functions to the
HCI core. This includes storing a list of IRKs per HCI device and the
ability to add, remove and lookup entries in that list.

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