Bluetooth: Remove unnecessary checks after canceling SMP security timer

The SMP security timer used to be able to modify the SMP context state
but now days it simply calls hci_disconnect(). It is therefore
unnecessary to have extra sanity checks for the SMP context after
canceling the timer.

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