uafs: avoid unnecessary type-punning

uafs: avoid unnecessary type-punning

There's no need to declare a separate buffer and initialize a structure
inside it when we can just instantiate the structure directly.

Change-Id: Idbcad31343ce7f074015f5921a4997d3f6c9799a
Reviewed-on: http://gerrit.openafs.org/7798
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>