CIFS: SMBD: Implement function to create a SMB Direct connection

The upper layer calls this function to connect to peer through SMB Direct.
Each SMB Direct connection is based on a RDMA RC Queue Pair.

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

fs/cifs/smbdirect.h

@@ -243,9 +243,15 @@ struct smbd_response {
 	u8 packet[];
 };
 
+/* Create a SMBDirect session */
+struct smbd_connection *smbd_get_connection(
+	struct TCP_Server_Info *server, struct sockaddr *dstaddr);
+
 #else
 #define cifs_rdma_enabled(server)	0
 struct smbd_connection {};
+static inline void *smbd_get_connection(
+	struct TCP_Server_Info *server, struct sockaddr *dstaddr) {return NULL;}
 #endif
 
 #endif