memory: mtk-smi: Add enable IOMMU SMC command for MM master

For concerns about security, the register to enable/disable IOMMU of
SMI LARB should only be configured in secure world. Thus, we add some
SMC command for multimedia master to enable/disable MM IOMMU in ATF by
setting the register of SMI LARB. This function is prepared for MT8188.

Signed-off-by: Chengci.Xu <chengci.xu@mediatek.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220817124608.10062-4-chengci.xu@mediatek.com