spi: dw-mmio: allow multiple instances

Use the platform_device id to uniquely identify each SPI master instance.

Cc: Jean-Hugues Deschenes <jean-hugues.deschenes@octasic.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Mark Brown <broonie@linaro.org>

drivers/spi/spi-dw-mmio.c

@@ -66,7 +66,7 @@ static int dw_spi_mmio_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
-	dws->bus_num = 0;
+	dws->bus_num = pdev->id;
 	dws->num_cs = 4;
 	dws->max_freq = clk_get_rate(dwsmmio->clk);