coda: Cache permisions in struct coda_inode_info in a kuid_t.

- Change c_uid in struct coda_indoe_info from a vuid_t to a kuid_t.
- Initialize c_uid to GLOBAL_ROOT_UID instead of 0.
- Use uid_eq to compare cached kuids.

Cc: Jan Harkes <jaharkes@cs.cmu.edu>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>