block: don't bloat enter_queue with percpu_ref

percpu_ref_put() are inlined for performance and bloat the binary, we
don't care about the fail case of blk_try_enter_queue(), so we can
replace it with a call to blk_queue_exit().

Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>