CIFS: SMBD: Upper layer connects to SMBDirect session

When "rdma" is specified in the mount option, make CIFS connect to
SMB Direct.

Signed-off-by: Long Li <longli@microsoft.com>
Signed-off-by: Steve French <smfrench@gmail.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>