ide-atapi: don't abuse rq->buffer

Impact: rq->buffer usage cleanup

ide-atapi uses rq->buffer as private opaque value for internal special
requests.  rq->special isn't used for these cases (the only case where
rq->special is used is for ide-tape rw requests).  Use rq->special
instead.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
diff --git a/drivers/ide/ide-atapi.c b/drivers/ide/ide-atapi.c
index 7201b17..2894577 100644
--- a/drivers/ide/ide-atapi.c
+++ b/drivers/ide/ide-atapi.c
@@ -90,7 +90,7 @@
 	blk_rq_init(NULL, rq);
 	rq->cmd_type = REQ_TYPE_SPECIAL;
 	rq->cmd_flags |= REQ_PREEMPT;
-	rq->buffer = (char *)pc;
+	rq->special = (char *)pc;
 	rq->rq_disk = disk;
 
 	if (pc->req_xfer) {
@@ -119,7 +119,7 @@
 
 	rq = blk_get_request(drive->queue, READ, __GFP_WAIT);
 	rq->cmd_type = REQ_TYPE_SPECIAL;
-	rq->buffer = (char *)pc;
+	rq->special = (char *)pc;
 
 	if (pc->req_xfer) {
 		rq->data = pc->buf;