arm64: dts: exynos: add syscon reboot/reboot_mode support in ExynosAutov9

arm64: dts: exynos: add syscon reboot/reboot_mode support in ExynosAutov9

Reboot of exynosautov9 SoC can be handled by setting the
bit(SWRESET_SYSTEM[1]) of SYSTEM_CONFIGURATION register(PMU + 0x3a00).
syscon-reboot-mode can be used to indicate the reboot mode for
bootloader. SYSIP_DAT0 register(PMU + 0x810) will not be cleared after
reboot so bootloader can enter the boot mode according to the value.

Signed-off-by: Chanho Park <chanho61.park@samsung.com>
Link: https://lore.kernel.org/r/20220523121244.67341-3-chanho61.park@samsung.com
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>