afs: remove redundant assignment

afs: remove redundant assignment

DRelease has two assignments for tp = entry->buffer; remove the second
(redundant) one.

Introduced with 0284e65f97861e888d95576f22a93cd681813c39 'dir: Explicitly
state buffer locations for data'.

No functional change should be incurred by this commit.

Change-Id: If4a17862f451973075fa3fa267b5139046d97ede
Reviewed-on: https://gerrit.openafs.org/13802
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Cheyenne Wills <cwills@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>