scsi: sd: Improve sd_completed_bytes

Re-shuffle the code to be more efficient by not initializing variables
upfront (i.e. do it only when necessary).  Also replace the do_div calls
with calls to sectors_to_logical().

No functional change is introduced by this patch.

[mkp: bytes_to_logical()]

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
diff --git a/drivers/scsi/sd.h b/drivers/scsi/sd.h
index 0cf9680..e6241c4 100644
--- a/drivers/scsi/sd.h
+++ b/drivers/scsi/sd.h
@@ -169,6 +169,11 @@ static inline unsigned int logical_to_bytes(struct scsi_device *sdev, sector_t b
 	return blocks * sdev->sector_size;
 }
 
+static inline sector_t bytes_to_logical(struct scsi_device *sdev, unsigned int bytes)
+{
+	return bytes >> ilog2(sdev->sector_size);
+}
+
 static inline sector_t sectors_to_logical(struct scsi_device *sdev, sector_t sector)
 {
 	return sector >> (ilog2(sdev->sector_size) - 9);