padata: add pd get/put refcnt helper

[ Upstream commit ae154202 ]

Add helpers for pd to get/put refcnt to make code consice.

Signed-off-by: Chen Ridong <chenridong@huawei.com>
Acked-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Stable-dep-of: dd7d37cc ("padata: avoid UAF for reorder_work")
Signed-off-by: Sasha Levin <sashal@kernel.org>