Implement Get POH Counter command

It returns a counter value proportional to the system operating
power-on hours.

Partially Resolves openbmc/openbmc#2979

Change-Id: Ib0cd43fe5cbc055ae84991577d766bedae58d775
Signed-off-by: Nagaraju Goruganti <ngorugan@in.ibm.com>
3 files changed