drivers: cpuidle: lpm-levels: Remove hotplug checking

This check doesn't make sense anymore because we're not entering
this code from hotplug paths anymore. Hotplug goes directly
through PSCI paths to the firmware. It used to be that we wanted
to handle the case where hotplug was happening but the cluster
was idle so we wanted to override the idle flag to consider the
cluster as idling instead of completely going away. But that
isn't true anymore with PSCI.

Change-Id: I6003fcfc6fa430fdadd3a9b82b789953b7a13a5f
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Maulik Shah <mkshah@codeaurora.org>