[SCSI] sr: remove dead code

This patch fixes an issue reported in drivers/scsi/sr.c by Coverity

Error reported: Pointer returned from "scsi_cd" is never used

Patch description:
 Remove the scsi_cd() call as it does not have any effect.

Signed-off-by: Jayachandran C. <c.jayachandran@gmail.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/sr.c

@@ -456,7 +456,7 @@ queue:
 static int sr_block_open(struct inode *inode, struct file *file)
 {
 	struct gendisk *disk = inode->i_bdev->bd_disk;
-	struct scsi_cd *cd = scsi_cd(inode->i_bdev->bd_disk);
+	struct scsi_cd *cd;
 	int ret = 0;
 
 	if(!(cd = scsi_cd_get(disk)))