smb: client: get rid of d_drop() in cifs_do_rename()

There is no need to force a lookup by unhashing the moved dentry after
successfully renaming the file on server.  The file metadata will be
re-fetched from server, if necessary, in the next call to
->d_revalidate() anyways.

Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
Reviewed-by: David Howells <dhowells@redhat.com>
Cc: stable@vger.kernel.org
Cc: linux-cifs@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>