blk-mq: fold __blk_mq_insert_req_list into blk_mq_insert_request

blk-mq: fold __blk_mq_insert_req_list into blk_mq_insert_request

Remove this very small helper and fold it into the only caller.

Note that this moves the trace_block_rq_insert out of ctx->lock, matching
the other calls to this tracepoint.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20230413064057.707578-9-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>