page_pool: Add function to batch and return stats

mainline inclusion
from mainline-v5.18-rc1
commit 6b95e338
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8BNYE
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6b95e3388b1ea0ca63500c5a6e39162dbf828433



----------------------------------------------------------------------

Adds a function page_pool_get_stats which can be used by drivers to obtain
stats for a specified page_pool.

Signed-off-by: Joe Damato <jdamato@fastly.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>