[CIFS] Finish up of case-insensitive dentry handling for cifs. This

will eventually (or should eventually) be common code for jfs, smbfs,
etc. but in the meantime is small enough and necessary when mounting
case insensitive to Windows (nocase).

Signed-off-by: Shaggy <(shaggy@austin.ibm.com)>
Signed-off-by: Steve French <(sfrench@us.ibm.com)>