mmc: sdhci-bcm2835: Actually enable the clock

We're currently using a fixed frequency clock specified in the DT, so
enabling is a no-op.  However, the RPi firmware-based clocks driver
can actually disable unused clocks, so when switching to use it we
ended up losing our MMC clock once all devices were probed.
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci-bcm2835.c

@@ -172,12 +172,19 @@ static int bcm2835_sdhci_probe(struct platform_device *pdev)
 		ret = PTR_ERR(pltfm_host->clk);
 		goto err;
 	}
+	ret = clk_prepare_enable(pltfm_host->clk);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to enable host clk\n");
+		goto err;
+	}
 
 	ret = sdhci_add_host(host);
 	if (ret)
-		goto err;
+		goto err_clk;
 
 	return 0;
+err_clk:
+	clk_disable_unprepare(pltfm_host->clk);
 err:
 	sdhci_pltfm_free(pdev);
 	return ret;