block: use blk_free_flush_queue() to free hctx->fq in blk_mq_init_hctx

block: use blk_free_flush_queue() to free hctx->fq in blk_mq_init_hctx

BugLink: https://bugs.launchpad.net/bugs/1838459
[ Upstream commit b9a1ff504b9492ad6beb7d5606e0e3365d4d8499 ]

kfree() can leak the hctx->fq->flush_rq field.

Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Shenghui Wang <shhuiw@foxmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>