smb: client: make use of smbdirect_connection_send_{single_iter,immediate_work}()

smb: client: make use of smbdirect_connection_send_{single_iter,immediate_work}()

With this the low level send functions are in common,
we'll have to do some more changes in generic smb code
in order to use smbdirect_connection_send_iter() instead
of looping around smbdirect_connection_send_single_iter().

David's cleanups will allow us to use
smbdirect_connection_send_iter().

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: David Howells <dhowells@redhat.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>