nfsd: revert v2 half of "nfsd: don't return high mode bits"

This reverts the part of commit 6e14b46b
that changes NFSv2 behavior.

Mark Lord found that it broke nfs-root for Linux clients, because it
broke NFSv2.

In fact, from RFC 1094:

	"Notice that the file type is specified both in the mode bits
	and in the file type.  This is really a bug in the protocol and
	will be fixed in future versions."

So NFSv2 clients really are expected to depend on the high bits of the
mode.

Cc: stable@kernel.org
Reported-by: NMark Lord <mlord@pobox.com>
Reviewed-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfsxdr.c

@@ -152,7 +152,7 @@ encode_fattr(struct svc_rqst *rqstp, __be32 *p, struct svc_fh *fhp,
 	type = (stat->mode & S_IFMT);
 
 	*p++ = htonl(nfs_ftypes[type >> 12]);
-	*p++ = htonl((u32) (stat->mode & S_IALLUGO));
+	*p++ = htonl((u32) stat->mode);
 	*p++ = htonl((u32) stat->nlink);
 	*p++ = htonl((u32) from_kuid(&init_user_ns, stat->uid));
 	*p++ = htonl((u32) from_kgid(&init_user_ns, stat->gid));