percpu: Convert remaining __get_cpu_var uses in 3.18-rcX

During the 3.18 merge period additional __get_cpu_var uses were
added. The patch converts these to this_cpu_ptr().

Signed-off-by: Christoph Lameter <cl@linux.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Tejun Heo <tj@kernel.org>