coda: remove struct coda_sb_info

The sb_info structure only contains a single pointer to the character device,
there is no need for the added indirection.

Signed-off-by: Jan Harkes <jaharkes@cs.cmu.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>