hw/arm/exynos: Check for CPU types in machine_run_board_init()

hw/arm/exynos: Check for CPU types in machine_run_board_init()

Restrict MachineClass::valid_cpu_types[] to the single
valid CPU type.

Instead of ignoring invalid CPU type requested by the user:

  $ qemu-system-arm -M nuri -cpu cortex-a7 -S -monitor stdio
  QEMU 8.2.50 monitor - type 'help' for more information
  (qemu) info qom-tree
  /machine (nuri-machine)
    /soc (exynos4210)
      /cpu[0] (cortex-a9-arm-cpu)
      ...

We now display an error:

  $ qemu-system-arm -M nuri -cpu cortex-a7
  qemu-system-arm: Invalid CPU model: cortex-a7
  The only valid type is: cortex-a9

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Message-id: 20240129151828.59544-3-philmd@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>