ath10k: fix dma_mapping_error() handling

The function returns 1 when DMA mapping fails. The
driver would return bogus values and could
possibly confuse itself if DMA failed.

Fixes: 767d34fc67 ("ath10k: remove DMA mapping wrappers")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

drivers/net/wireless/ath/ath10k/htc.c

@@ -145,8 +145,10 @@ int ath10k_htc_send(struct ath10k_htc *htc,
 	skb_cb->eid = eid;
 	skb_cb->paddr = dma_map_single(dev, skb->data, skb->len, DMA_TO_DEVICE);
 	ret = dma_mapping_error(dev, skb_cb->paddr);
-	if (ret)
+	if (ret) {
+		ret = -EIO;
 		goto err_credits;
+	}
 
 	sg_item.transfer_id = ep->eid;
 	sg_item.transfer_context = skb;