cifs: fix return of uninitialized rc in dfs_cache_update_tgthint()

Fix this by initializing rc to 0 as cache_refresh_path() would not set
it in case of success.

Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/all/202301190004.bEHvbKG6-lkp@intel.com/


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