coda: coda doesn't track atime

Set MS_NOATIME flag to avoid unnecessary calls when the coda inode is
accessed.

Also, set statfs.f_bsize to 4k.  1k is obviously too small for the suggested
IO size.

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>