quota: add new helper dquot_active()

[ Upstream commit 33bcfafc48cb186bc4bbcea247feaa396594229e ]

Add new helper function dquot_active() to make the code more concise.

Signed-off-by: Baokun Li <libaokun1@huawei.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <20230630110822.3881712-4-libaokun1@huawei.com>
Stable-dep-of: dabc8b207566 ("quota: fix dqput() to follow the guarantees dquot_srcu should provide")
Signed-off-by: Sasha Levin <sashal@kernel.org>