Simplify cnfs.c

[Katsuhiro Kondou]

In article <72k87rfmpo.fsf at nd1.eng.demon.net>,
	Alex Kiernan <alexk at demon.net> wrote;

} This patch removes the dual mmap/write stuff for the header/bitmap &
} just uses mmap. AFAICT this shouldn't cause regression on other
} platforms as you need mmap to work to get cnfs anyway.
} 
} Ultimately the patch adds no real value though...

Looks reasonable except error handling(need to unmap
in CNFSinit_disks()).  I'll probably apply with some
with its fix after current work.
-- 
Katsuhiro Kondou