cifs: Move cached-dir functions into a separate file

Also rename crfid to cfid to have consistent naming for this variable.

This commit does not change any logic.

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>