drivers: cpuidle: lpm-levels: Move local_irq_enable

Cancelling histtimer after enabling local irqs can cause
low sleep length to get calculated during next low power mode
entry.

Enable local irqs after cancelling histtimer.
Use hrtimer_get_remaining before cancelling timer.

Change-Id: I735770f779c5760acc6b62cb65811b21244d0e99
Signed-off-by: Maulik Shah <mkshah@codeaurora.org>