memory: tegra186-emc: Handle errors in BPMP response

The return value from tegra_bpmp_transfer indicates the success or
failure of the IPC transaction with BPMP. If the transaction
succeeded, we also need to check the actual command's result code.
Add code to do this.

Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Link: https://lore.kernel.org/r/20210915085517.1669675-3-mperttunen@nvidia.com


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>