xfs: remove old and redundant comment in xfs_mount_validate_sb

The error messages document the reason for the checks better than the comment
and the comments about volume mounts date back to Irix and so aren't relevant
any more. So just remove the old and redundant comment.
Signed-off-by: Wang Sheng-Hui <shhuiw@foxmail.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/libxfs/xfs_sb.c

@@ -111,14 +111,6 @@ xfs_mount_validate_sb(
 	bool		check_inprogress,
 	bool		check_version)
 {
-
-	/*
-	 * If the log device and data device have the
-	 * same device number, the log is internal.
-	 * Consequently, the sb_logstart should be non-zero.  If
-	 * we have a zero sb_logstart in this case, we may be trying to mount
-	 * a volume filesystem in a non-volume manner.
-	 */
 	if (sbp->sb_magicnum != XFS_SB_MAGIC) {
 		xfs_warn(mp, "bad magic number");
 		return -EWRONGFS;