Machine core patches

- Rework SMP parsing unit test to work on WinGW:

  https://github.com/qemu/qemu/runs/4078386652

  This fixes:

    Test smp_parse failed!
    Expected error report: Invalid SMP CPUs 1. The min CPUs supported by machine '(null)' is 2
      Output error report: Invalid SMP CPUs 1. The min CPUs supported by machine '(NULL)' is 2

# gpg: Signature made Mon 15 Nov 2021 11:46:36 PM CET
# gpg:                using RSA key FAABE75E12917221DCFD6BB2E3E32C2CDEADC0DE
# gpg: Good signature from "Philippe Mathieu-Daudé (F4BUG) <f4bug@amsat.org>" [full]

* tag 'machine-core-20211115' of https://github.com/philmd/qemu

:
  tests/unit/test-smp-parse: Explicit MachineClass name
  tests/unit/test-smp-parse: QOM'ify smp_machine_class_init()
  tests/unit/test-smp-parse: Restore MachineClass fields after modifying

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>