cifs: Fix oops due to uncleared server->smbd_conn in reconnect

cifs: Fix oops due to uncleared server->smbd_conn in reconnect

commit b7ab9161cf5ddc42a288edf9d1a61f3bdffe17c7 upstream.

In smbd_destroy(), clear the server->smbd_conn pointer after freeing the
smbd_connection struct that it points to so that reconnection doesn't get
confused.

Fixes: 2cb924bb40fd ("CIFS: SMBD: Implement function to destroy a SMB Direct connection")
Cc: stable@vger.kernel.org
Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Acked-by: Tom Talpey <tom@talpey.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Long Li <longli@microsoft.com>
Cc: Pavel Shilovsky <piastryyy@gmail.com>
Cc: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>