Linux: 2.6.38: dentry->d_count is not an atomic

Linux: 2.6.38: dentry->d_count is not an atomic

d_count is now an int protected by the dentry's d_lock.
Take the lock when we use it, instead of using an atomic_*
function.

Reviewed-on: http://gerrit.openafs.org/3883
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 281f5bf5fbb0a546edcce62ef4e097ae9bbdbf73)

Change-Id: Id30054cb110720632f6f4a7fc4d7860cb69cb1e7
Signed-off-by: Anders Kaseorg <andersk@mit.edu>
Reviewed-on: http://gerrit.openafs.org/3999
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Russ Allbery <rra@stanford.edu>
(cherry picked from commit fe8d833e53938319d1fb6e20153a50a74bed5860)