scsi: use correct API to get request position and size

Let sd driver use correct API to get request position and size.

---
 drivers/scsi/sd.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

Index: linux/drivers/scsi/sd.c
===================================================================
@@ -539,9 +539,8 @@ static void sd_config_discard(struct scs
 static int scsi_setup_discard_cmnd(struct scsi_device *sdp, struct 

request *rq)
{
struct scsi_disk *sdkp = scsi_disk(rq->rq_disk);
- struct bio *bio = rq->bio;
- sector_t sector = bio->bi_sector;
- unsigned int nr_sectors = bio_sectors(bio);
+ sector_t sector = blk_rq_pos(rq);
+ unsigned int nr_sectors = blk_rq_sectors(rq);
unsigned int len;
int ret;
char *buf;