mmc: meson-gx: add device reset

Trigger the reset line of the mmc controller while probing, if available.
The reset should be optional for now, at least until all related DT nodes
have the reset property.
Reviewed-by: NKevin Hilman <khilman@baylibre.com>
Signed-off-by: NJerome Brunet <jbrunet@baylibre.com>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/meson-gx-mmc.c

@@ -35,6 +35,7 @@
 #include <linux/clk.h>
 #include <linux/clk-provider.h>
 #include <linux/regulator/consumer.h>
+#include <linux/reset.h>
 #include <linux/interrupt.h>
 #include <linux/bitfield.h>
 #include <linux/pinctrl/consumer.h>
@@ -1212,6 +1213,14 @@ static int meson_mmc_probe(struct platform_device *pdev)
 		goto free_host;
 	}
 
+	ret = device_reset_optional(&pdev->dev);
+	if (ret) {
+		if (ret != -EPROBE_DEFER)
+			dev_err(&pdev->dev, "device reset failed: %d\n", ret);
+
+		return ret;
+	}
+
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	host->regs = devm_ioremap_resource(&pdev->dev, res);
 	if (IS_ERR(host->regs)) {