spi: rspi: Configure DMA slave bus width to 8 bit

The new Renesas R-Car Gen2 DMA Controller driver (rcar-dmac) requires
explicit configuration of the DMA slave bus width.
Hardcode the DMA transfer size to 1 byte for both directions, as that's
the only supported configuration (16-bit DMA support was removed in
commit 9c5de2c1754c2bb3c69c4d7bf0d0edc0a61d8232 ("spi: rspi: Remove
unused 16-bit DMA support")).

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Mark Brown <broonie@linaro.org>

drivers/spi/spi-rspi.c

@@ -919,10 +919,13 @@ static struct dma_chan *rspi_request_dma_chan(struct device *dev,
 	memset(&cfg, 0, sizeof(cfg));
 	cfg.slave_id = id;
 	cfg.direction = dir;
-	if (dir == DMA_MEM_TO_DEV)
+	if (dir == DMA_MEM_TO_DEV) {
 		cfg.dst_addr = port_addr;
-	else
+		cfg.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+	} else {
 		cfg.src_addr = port_addr;
+		cfg.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+	}
 
 	ret = dmaengine_slave_config(chan, &cfg);
 	if (ret) {