arm64: dts: exynos: Add initial support for the Exynos 990 SoC

arm64: dts: exynos: Add initial support for the Exynos 990 SoC

The Exynos 990 SoC is an ARMv8 mobile SoC found in Samsung Galaxy N/S20
series phones (x1sxxx, c1sxxx). Add minimal support for this SoC,
including:

- All 8 cores via PSCI
- ChipID
- Generic timer.
- Pinctrl

The devices using this SoC suffer from the same issue as Exynos 8895
caused by the stock Samsung bootloader, as it doesn't configure
CNTFRQ_EL0. Hence it's needed to hardcode the adequate frequency in the
timer node, otherwise the kernel panics.

Signed-off-by: Igor Belwon <igor.belwon@mentallysanemainliners.org>
Link: https://lore.kernel.org/r/20241016154747.64343-6-igor.belwon@mentallysanemainliners.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>