libafs: fix some nits around the symlink VOP

Commit 3f4c1099b7b (gerrit 10474) introduced a few issues, addressed here.

vpp is idiomatically of type 'struct vnode *', not 'struct vcache *';
use pvc as the name of the parent vcache pointer instead.

Fix whitespace.

Change-Id: Ic5d98a43446861bb571fe5a260e7ae1eea1051fd
Reviewed-on: http://gerrit.openafs.org/10531
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>