afs: define NUMPAGGROUPS once

afs: define NUMPAGGROUPS once

Define the number of groups per PAG in one place.  Prefix the define
with AFS_ to avoid name conflicts in the future (unlikely as it may be).

Fix the misnamed AFSPAGGGROUPS symbol in linux implementation of two
groups per PAG.

Reviewed-on: https://gerrit.openafs.org/12382
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit b39095c3a7e1c631bb17816b7e707bc21a6b8c71)

Change-Id: I8e0531e9a7e2fc1f3d1eb8255c75ecd758dbce9a
Reviewed-on: https://gerrit.openafs.org/12524
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>