Bluetooth: Don't take any action in smp_resume_cb if not encrypted

When smp_resume_cb is called if we're not encrypted (i.e. the callback
wasn't called because the connection became encrypted) we shouldn't take
any action at all. This patch moves also the security_timer cancellation
behind this condition.

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