Revert "osi_UFSOpen returns struct osi_file *"

Revert "osi_UFSOpen returns struct osi_file *"

This reverts commit 4057a9941b95f7a00c57738c1810ec5abf315e97.

UFSOpen shares a prototype with MemCacheOpen because of the
afs_cacheOps structure.  This is why a void * is used.
Revert until a more complete fix can be submitted that adresses
the memcache case as well.

Change-Id: I2e259c08a0bfbc695260c981d29319c2bb7c93dd
Reviewed-on: http://gerrit.openafs.org/865
Reviewed-by: Simon Wilkinson <sxw@inf.ed.ac.uk>
Tested-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>