block: implement blk_rq_pos/[cur_]sectors() and convert obvious ones

Implement accessors - blk_rq_pos(), blk_rq_sectors() and
blk_rq_cur_sectors() which return rq->hard_sector, rq->hard_nr_sectors
and rq->hard_cur_sectors respectively and convert direct references of
the said fields to the accessors.

This is in preparation of request data length handling cleanup.

Geert	: suggested adding const to struct request * parameter to accessors
Sergei	: spotted error in patch description

[ Impact: cleanup ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Acked-by: Stephen Rothwell <sfr@canb.auug.org.au>
Tested-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Ackec-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Cc: Borislav Petkov <petkovbb@googlemail.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/drivers/ide/ide-cd.c b/drivers/ide/ide-cd.c
index 8bbe222..182320d 100644
--- a/drivers/ide/ide-cd.c
+++ b/drivers/ide/ide-cd.c
@@ -730,7 +730,7 @@
 		if (blk_pc_request(rq))
 			nsectors = (rq->data_len + 511) >> 9;
 		else
-			nsectors = rq->hard_nr_sectors;
+			nsectors = blk_rq_sectors(rq);
 
 		if (nsectors == 0)
 			nsectors = 1;
@@ -875,7 +875,7 @@
 
 	return ide_issue_pc(drive, &cmd);
 out_end:
-	nsectors = rq->hard_nr_sectors;
+	nsectors = blk_rq_sectors(rq);
 
 	if (nsectors == 0)
 		nsectors = 1;
@@ -1359,8 +1359,8 @@
 static int ide_cdrom_prep_fs(struct request_queue *q, struct request *rq)
 {
 	int hard_sect = queue_hardsect_size(q);
-	long block = (long)rq->hard_sector / (hard_sect >> 9);
-	unsigned long blocks = rq->hard_nr_sectors / (hard_sect >> 9);
+	long block = (long)blk_rq_pos(rq) / (hard_sect >> 9);
+	unsigned long blocks = blk_rq_sectors(rq) / (hard_sect >> 9);
 
 	memset(rq->cmd, 0, BLK_MAX_CDB);