coda: remove CODA_FS_OLD_API

While fixing CONFIG_ leakages to the userspace kernel headers I ran into
CODA_FS_OLD_API.

After five years, are there still people using the old API left?
Especially considering that you have to choose at compile time which API
to support in the kernel (and distributions tend to offer the new API for
some time).

Jan: "The old API can definitely go.  Around the time the new
      interface went in there were some non-Coda userspace file system
      implementations that took a while longer to convert to the new API,
      but by now they all switched to the new interface or in some cases
      to a FUSE-based solution."

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Acked-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>