hw/arm/exynos: Fix proper mapping of CPUs by providing real cluster ID

The Exynos4210 has cluster ID 0x9 in its MPIDR register (raw value
0x8000090x).  If this cluster ID is not provided, then Linux kernel
cannot map DeviceTree nodes to MPIDR values resulting in kernel
warning and lack of any secondary CPUs:

    DT missing boot CPU MPIDR[23:0], fall back to default cpu_logical_map
    ...
    smp: Bringing up secondary CPUs ...
    smp: Brought up 1 node, 1 CPU
    SMP: Total of 1 processors activated (24.00 BogoMIPS).

Provide a cluster ID so Linux will see proper MPIDR and will try to
bring the secondary CPU online.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Message-id: 20170226200142.31169-2-krzk@kernel.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>