Linux 3.6: d_alias and i_dentry are now hlists

Linux 3.6: d_alias and i_dentry are now hlists

The d_alias pointer is now the head of an hlist.  This means the
iterator is a different macro and has no "reverse" version since
hlists have no direct pointer to the list tail.

inode->i_dentry gets the same treatment.  Adjust where we use it.

Reviewed-on: http://gerrit.openafs.org/7983
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>
(cherry picked from commit 6bea047fb404bde828c6358ae06f7941aa2bc959)

Change-Id: I7e7b87e5f5c240f3f0ff25fa723c857ab9d0108c
Reviewed-on: http://gerrit.openafs.org/8080
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Ken Dreyer <ktdreyer@ktdreyer.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>