percpu: Replace __get_cpu_var with this_cpu_ptr

__this_cpu_ptr is being phased out.  Use raw_cpu_ptr instead which was
introduced in 3.15-rc1.  One case of using __get_cpu_var in the
get_cpu_var macro for address calculation was remaining in
include/linux/percpu.h.

tj: Updated patch description.

Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

include/linux/percpu.h

@@ -29,7 +29,7 @@
  */
 #define get_cpu_var(var) (*({				\
 	preempt_disable();				\
-	&__get_cpu_var(var); }))
+	this_cpu_ptr(&var); }))
 
 /*
  * The weird & is necessary because sparse considers (void)(var) to be