smb: client: make use of smbdirect_socket.send_io.lcredits.*

smb: client: make use of smbdirect_socket.send_io.lcredits.*

This makes the logic to prevent on overflow of
the send submission queue with ib_post_send() easier.

As we first get a local credit and then a remote credit
before we mark us as pending.

For now we'll keep the logic around smbdirect_socket.send_io.pending.*,
but that will likely change or be removed completely.

The server will get a similar logic soon, so
we'll be able to share the send code in future.

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>
Signed-off-by: Steve French <stfrench@microsoft.com>