cifs: Fix a tiny potential memory leak

The most recent "it" allocation is leaked on this error path.  I
believe that small allocations always succeed in current kernels so
this doesn't really affect run time.

Fixes: 54be1f6c ("cifs: Add DFS cache routines")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steve French <stfrench@microsoft.com>