Return the error code when command fails.

Fixes: 13324edb ("memory: tegra186-emc: Handle errors in BPMP response")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Mikko Perttunen <mperttunen@nvidia.com>
Link: https://lore.kernel.org/r/20210928021545.3774677-1-yangyingliang@huawei.comSigned-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>