nvmet-tcp: fix data digest pointer calculation

exp_ddgst is of type __le32, &cmd->exp_ddgst + cmd->offset increases
&cmd->exp_ddgst by 4 * cmd->offset, fix this by type casting
&cmd->exp_ddgst to u8 *.

Fixes: 872d26a3 ("nvmet-tcp: add NVMe over TCP target driver")
Signed-off-by: Varun Prakash <varun@chelsio.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/target/tcp.c

@@ -702,7 +702,7 @@ static int nvmet_try_send_ddgst(struct nvmet_tcp_cmd *cmd, bool last_in_batch)
 	struct nvmet_tcp_queue *queue = cmd->queue;
 	struct msghdr msg = { .msg_flags = MSG_DONTWAIT };
 	struct kvec iov = {
-		.iov_base = &cmd->exp_ddgst + cmd->offset,
+		.iov_base = (u8 *)&cmd->exp_ddgst + cmd->offset,
 		.iov_len = NVME_TCP_DIGEST_LENGTH - cmd->offset
 	};
 	int ret;