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: Mark Lord <mlord@pobox.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>