msm: Remove idle stats and cpuidle hooks

Calling RCU functions from within the RCU quiescent state is
illegal and probably a bug. The idlestats code uses an atomic
notifier called from msm_cpuidle_enter() and that atomic notifier
takes an rcu read lock. We could fix this with a raw notifier,
but this code is unused so let's just remove the code entirely.

Change-Id: I319f0eabb56a8721c19a3b2b4bc9a7f416c88384
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>