mmc: sdhci: Do not BUG on invalid vdd

BugLink: http://bugs.launchpad.net/bugs/1520454

The driver may not be able to set the power correctly but that
is not a reason to BUG().
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Venu Byravarasu <vbyravarasu@nvidia.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
(cherry picked from commit 9d5de93f)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/mmc/host/sdhci.c

@@ -1304,7 +1304,9 @@ static void sdhci_set_power(struct sdhci_host *host, unsigned char mode,
 			pwr = SDHCI_POWER_330;
 			break;
 		default:
-			BUG();
+			WARN(1, "%s: Invalid vdd %#x\n",
+			     mmc_hostname(host->mmc), vdd);
+			break;
 		}
 	}