lpm-levels: Read next hrtimer event after tick_nohz_idle_stop_tick()

idle_tick is a periodic timer which sends the interrupt to cpu
for every jiffy. If next event is read before stopping the cpu
idle_tick it gives the next tick expiry time as the next event.
Current logic reading the cpu next event time before stopping
the idle tick gives shallower sleep length recorded. This prevents
cluster low power mode to get selected since next wakeup is seen
either very near to current time or as already expired.

Fix this to read next event after idle_tick has been stopped.

Change-Id: I8016c7911dc48450668a8a6bc7a6d01d4423da32
Signed-off-by: Raghavendra Kakarla <rkakarla@codeaurora.org>