Bluetooth: Add identity address check in param lookup functions

Since we only store entries with identity addresses in the
le_conn_params and pend_le_conns lists we can avoid unnecessary lookups
by checking for an identity address before diving into the lists
themselves.

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