mmc: dw_mmc: Indicate that regulators may be absent

Use regulator_get_optional() to tell the core that requests for regulators
can fail in a real system.

Signed-off-by: Mark Brown <broonie@linaro.org>
Acked-by: Chris Ball <cjb@laptop.org>
Acked-by: Seungwon Jeon <tgih.jun@samsung.com>
Acked-by: Jaehoon Chung <jh80.chung@samsung.com>

drivers/mmc/host/dw_mmc.c

@@ -2231,7 +2231,7 @@ int dw_mci_probe(struct dw_mci *host)
 		}
 	}
 
-	host->vmmc = devm_regulator_get(host->dev, "vmmc");
+	host->vmmc = devm_regulator_get_optional(host->dev, "vmmc");
 	if (IS_ERR(host->vmmc)) {
 		ret = PTR_ERR(host->vmmc);
 		if (ret == -EPROBE_DEFER)