cpuidle: lpm-levels: Fix RIMPS timer programming

For the hotplug case there is chance that RIMPS timer being
programmed even if the last core in the domain is going down.
Consider online state of cpu's to fix this.

Change-Id: Id2bdd99c0e93ea67d5c9a1ae77fa033f004809c9
Signed-off-by: Srinivas Rao L <lsrao@codeaurora.org>