Bluetooth: Fix completing SMP as peripheral when no keys are expected

When we're the acceptors (peripheral/slave) of an SMP procedure and
we've completed distributing our keys we should only stick around
waiting for keys from the remote side if any of the initiator
distribution bits were actually set. This patch fixes the
smp_distribute_keys function to clear the SMP context when this
situation occurs.

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