ufs: move non-layout parts of ufs_fs.h to fs/ufs/

Move prototypes and in-core structures to fs/ufs/ similar to what most
other filesystems already do.

I made little modifications: move also ufs debug macros and
mount options constants into fs/ufs/ufs.h, this stuff
also private for ufs.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Evgeniy Dushistov <dushistov@mail.ru>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>