Bluetooth: Check for matching IRK when looking for paired LE devices

If we're given an RPA when checking whether we're paired or not, we
should consult the local RPA storage whether there's a matching IRK.
This we we ensure that hci_bdaddr_is_paired() gives the right result
even when trying to pair a second time with the same device with an RPA.

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