arm64: defconfig: Enable CIX SoC

- Enable CIX SoC support at ARM64 defconfig
- Enable CIX mailbox
At CIX SoC platforms, the clock handling uses Arm SCMI protocol,
the physical clock access is at sub processor, so it needs to enable
mailbox by default.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Peter Chen <peter.chen@cixtech.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Author: Peter Chen

arch/arm64/configs/defconfig

@@ -45,6 +45,7 @@ CONFIG_ARCH_BCMBCA=y
 CONFIG_ARCH_BRCMSTB=y
 CONFIG_ARCH_BERLIN=y
 CONFIG_ARCH_BLAIZE=y
+CONFIG_ARCH_CIX=y
 CONFIG_ARCH_EXYNOS=y
 CONFIG_ARCH_SPARX5=y
 CONFIG_ARCH_K3=y
@@ -1410,6 +1411,7 @@ CONFIG_BCM2835_MBOX=y
 CONFIG_QCOM_APCS_IPC=y
 CONFIG_MTK_ADSP_MBOX=m
 CONFIG_QCOM_IPCC=y
+CONFIG_CIX_MBOX=y
 CONFIG_ROCKCHIP_IOMMU=y
 CONFIG_TEGRA_IOMMU_SMMU=y
 CONFIG_ARM_SMMU=y