1. do not allow external modules to touch internal field of a timer.
2. make timer mode internal, period_in_ticks will decide the mode.
API wise:
1. the "mode" parameter was taken out of initialize_timer().
2. a new function update_timer() was added to update the timeout and
period fields.
3. the timer_expired() function was extended with an output parameter
to return the remaining cycles before expiration.
Also, the "fire_tsc" field name of hv_timer was renamed to "timeout".
With the new API, however, this change should not concern user code.
Tracked-On: #5920
Signed-off-by: Jason Chen CJ <jason.cj.chen@intel.com>
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