block: Replace __this_cpu_ptr with raw_cpu_ptr

__this_cpu_ptr is being phased out use raw_cpu_ptr instead which was
introduced in 3.15-rc1.

Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

fs/ext4/mballoc.c

@@ -4129,7 +4129,7 @@ static void ext4_mb_group_or_file(struct ext4_allocation_context *ac)
 	 * per cpu locality group is to reduce the contention between block
 	 * request from multiple CPUs.
 	 */
-	ac->ac_lg = __this_cpu_ptr(sbi->s_locality_groups);
+	ac->ac_lg = raw_cpu_ptr(sbi->s_locality_groups);
 
 	/* we're going to use group allocation */
 	ac->ac_flags |= EXT4_MB_HINT_GROUP_ALLOC;