cpuidle: Inform RCU of read-side critical sections

From: "Paul E. McKenney" <paul.mckenney@linaro.org>

The cpuidle_idle_call() function is invoked in the inner idle loop,
after the call to rcu_idle_enter() and before the call to rcu_idle_exit().
This means that RCU is ignoring the CPU at this point.  Unfortunately,
cpuidle_idle_call() nevertheless contains tracepoints (important ones
used by powertop) that expect RCU to be paying attention.  The consequences
of using RCU read-side critical sections on CPUs that RCU is ignoring
can be severe, including random corruption of random memory.

Therefore, this commit uses the new RCU_NONIDLE() macro to let RCU
do its job with respect to the tracepoints.

Suggested-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Trinabh Gupta <g.trinabh@gmail.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
modified by faux123