mmc: sdhci: Do not BUG on invalid vdd

[ Upstream commit 9d5de93f ]

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>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>