Bluetooth: Look up RPA for connection requests with Identity Address

We need to check whether there's a matching IRK and RPA when we're
requested to connect to a remote LE device based on its Identity
Address. This patch updates the hci_connect_le function to do an extra
call to hci_find_irk_by_addr and uses the RPA if it's cached. This is
particularly important once we start exposing the Identity Address to
user space instead of the RPA in events such as Device Connected and
Device Found.

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