blk-mq: update ->init_request and ->exit_request prototypes

Remove the request_idx parameter, which can't be used safely now that we
support I/O schedulers with blk-mq.  Except for a superflous check in
mtip32xx it was unused anyway.

Also pass the tag_set instead of just the driver data - this allows drivers
to avoid some code duplication in a follow on cleanup.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 994403e..28d9329 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1697,9 +1697,8 @@
 	loop_handle_cmd(cmd);
 }
 
-static int loop_init_request(void *data, struct request *rq,
-		unsigned int hctx_idx, unsigned int request_idx,
-		unsigned int numa_node)
+static int loop_init_request(struct blk_mq_tag_set *set, struct request *rq,
+		unsigned int hctx_idx, unsigned int numa_node)
 {
 	struct loop_cmd *cmd = blk_mq_rq_to_pdu(rq);