smb: smbdirect: introduce smbdirect_socket_shutdown()

smb: smbdirect: introduce smbdirect_socket_shutdown()

This can be used by client and server to trigger a
disconnect of the connection, the idea of to be
similar to kernel_sock_shutdown(), but for smbdirect
there's no point in shutting down only one direction
so there's no 'how' argument.

Cc: Steve French <smfrench@gmail.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Long Li <longli@microsoft.com>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>