blk-cgroup: cleanup the blkg_lookup family of functions

blk-cgroup: cleanup the blkg_lookup family of functions

[ Upstream commit 4a69f325aa43847e0827fbfe4b3623307b0c9baa ]

Add a fully inlined blkg_lookup as the extra two checks aren't going
to generated a lot more code vs the call to the slowpath routine, and
open code the hint update in the two callers that care.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Andreas Herrmann <aherrmann@suse.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220921180501.1539876-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Stable-dep-of: 813e693023ba ("blk-iolatency: Fix memory leak on add_disk() failures")
Signed-off-by: Sasha Levin <sashal@kernel.org>