rx: Remove dead AFS_ADAPT_PMTU SUN5 code
AFS_ADAPT_PMTU is only defined on linux26, so anything which is
conditional on both AFS_ADAPT_PMTU and AFS_SUN5_ENV being set is
dead code.
This seems to have been dead code since its introduction in
commit
1206e7538be86f073b21cd289266286b60a95d0a.
Change-Id: I9bb6ff40de87a7f2d8d953ef7583c6c2b090ab48
Reviewed-on: http://gerrit.openafs.org/11631
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Reviewed-by: Daria Brashear <shadow@your-file-system.com>