As part of the reset process, save the current tick count to an
uninitialized memory location. That way, the current tick value will be
preserved across reboots.
A reboot will cause us to lose a certain number of ticks, depending on
how long a reboot takes, however if reboots are infrequent then this
will not be a large amount of time lost.
Signed-off-by: Sean Cross <sean@xobs.io>