blkcg: allow blkcg_policy->pd_stat() to print non-debug info too

Currently, ->pd_stat() is called only when moduleparam
blkcg_debug_stats is set which prevents it from printing non-debug
policy-specific statistics.  Let's move debug testing down so that
->pd_stat() can print non-debug stat too.  This patch doesn't cause
any visible behavior change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>