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).

Change-Id: I9d738bdd528577d0a7ccd307246b5e935379c84d
Reviewed-on: http://gerrit.openafs.org/3758
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>