drivers: cpuidle: lpm-levels: Fixes for clockevents_notify

The use of clockevents_notify is deprecated and targeted APIs are used
instead of the clockevents_notify callbacks. Switch broadcast timer
notifications to tick_broadcast_enter and tick_broadcast_exit.

Change-Id: I3441873eb4009b105db04f4a18d28ae9ccd07e95
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>