smb: server: make use of smbdirect_socket.idle.immediate_work

smb: server: make use of smbdirect_socket.idle.immediate_work

With this commit the server only uses struct smbdirect_socket!

It doesn't use the idle timer yet, but it will be added soon,
from there we'll be ready split common functions.

Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Steve French <smfrench@gmail.com>
Cc: Tom Talpey <tom@talpey.com>
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>