Linux: 3.1: update RCU path walking detection in permission i_op

Linux: 3.1: update RCU path walking detection in permission i_op

The permission() inode operation changed again with kernel 3.1,
back to the form it had before 2.6.38.  This compiles fine,
but is missing the new way of detecting when we get called in
RCU path walking mode, resulting in system hangs.

Reviewed-on: http://gerrit.openafs.org/5740
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>
(cherry picked from commit 4952df3f0359531e4a660c99c94c51eb0b169f59)

Change-Id: Ibd497309e6699fb585cf70e618373e800b73cbb8
Reviewed-on: http://gerrit.openafs.org/6088
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>