Bluetooth: Handle command complete event for HCI Read Stored Link Keys

When the HCI Read Stored Link Keys command completes it gives useful
information of the current stored keys and maximum keys a controller
can actually store. So process this event and store these information
in hci_dev structure.

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