linux: 2.6.38: New d_op handling

linux: 2.6.38: New d_op handling

In 2.6.38, the super block structure has a new field to hold the
default dentry ops.  The vfs will automatically set it for new
dentries in most cases.

Set s_d_op to our set of operations, and omit setting the dentry
ops where the vfs will already do it (and where new locking rules
prohibit it).

Reviewed-on: http://gerrit.openafs.org/3758
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 08bb83d95027bb3ac68834d12b72bdc647fa24a9)

Change-Id: I15affd47c02653b3b46a0c97e64d06ba4ecbac1c
Signed-off-by: Anders Kaseorg <andersk@mit.edu>
Reviewed-on: http://gerrit.openafs.org/3994
Reviewed-by: Simon Wilkinson <sxw@inf.ed.ac.uk>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Marc Dionne <marc.c.dionne@gmail.com>
Reviewed-by: Russ Allbery <rra@stanford.edu>
(cherry picked from commit 0d95e6b800044f9cfa6dd4057477394c3a9cc44d)