xfs: Do not return EFSCORRUPTED when filesystem probe finds no XFS magic

98021821 changed the return value from EWRONGFS (aka EINVAL)
to EFSCORRUPTED which doesn't seem to be handled properly by
the root filesystem probe.
Signed-off-by: NEric Sandeen <sandeen@redhat.com>
Tested-by: NSergei Trofimovich <slyfox@gentoo.org>
Reviewed-by: NBen Myers <bpm@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

fs/xfs/xfs_mount.c

@@ -658,7 +658,7 @@ xfs_sb_quiet_read_verify(
 		return;
 	}
 	/* quietly fail */
-	xfs_buf_ioerror(bp, EFSCORRUPTED);
+	xfs_buf_ioerror(bp, EWRONGFS);
 }
 
 static void