dma_map_sg return 0 on error, fix the error check, and return -EIO
to caller.
Fixes: dbc049eee730 ("mailbox: Add driver for Broadcom FlexRM ring manager")
Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>
 
        rc = dma_map_sg(dev, msg->spu.src, sg_nents(msg->spu.src),
                        DMA_TO_DEVICE);
-       if (rc < 0)
-               return rc;
+       if (!rc)
+               return -EIO;
 
        rc = dma_map_sg(dev, msg->spu.dst, sg_nents(msg->spu.dst),
                        DMA_FROM_DEVICE);
-       if (rc < 0) {
+       if (!rc) {
                dma_unmap_sg(dev, msg->spu.src, sg_nents(msg->spu.src),
                             DMA_TO_DEVICE);
-               return rc;
+               return -EIO;
        }
 
        return 0;