[SCSI] st: Fixup -ENOMEDIUM

Based on the original patch from Hannes Reinecke <hare@suse.de>

Fix st_open() to return -ENOMEDIUM instead of -EIO if no medium is
found.
Signed-off-by: Kai Makisara <kai.makisara@kolumbus.fi>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/st.c

@@ -1177,6 +1177,9 @@ static int st_open(struct inode *inode, struct file *filp)
 		goto err_out;
 	if ((filp->f_flags & O_NONBLOCK) == 0 &&
 	    retval != CHKRES_READY) {
+		if (STp->ready == NO_TAPE)
+			retval = (-ENOMEDIUM);
+		else
 			retval = (-EIO);
 		goto err_out;
 	}