timer: tickless: hpet: Add tickless kernel support

Update the timer to use the tickless kernel interface
provided by kernel to operate in event based mode. In
this mode, the timer would not generate periodic ticks
and would only be programmed in one shot mode. It would
announce elapsed time in wall time units instead of
ticks. Timer can also be disabled enabling waiting
forever for a non-timer event.

Jira: ZEP-1812
Change-Id: I13110b9fb53b33a9244cc91a3d991f8452d330b1
Signed-off-by: Ramesh Thomas <ramesh.thomas@intel.com>