Merge remote-tracking branch 'afaerber/qom-cpu' into staging

# By Andreas Färber
# Via Andreas Färber
* afaerber/qom-cpu:
  linux-user: bsd-user: Don't reset X86CPU twice
  target-i386: Pass X86CPU to cpu_x86_set_a20()
  target-unicore32: Rename CPU subtypes
  target-openrisc: Rename CPU subtypes
  target-openrisc: TYPE_OPENRISC_CPU should be abstract
  target-m68k: Rename CPU subtypes
  target-m68k: Mark as unmigratable
  target-s390x: Mark as unmigratable
  target-sh4: Mark as unmigratable
  target-xtensa: Mark as unmigratable
  target-microblaze: Mark as unmigratable
  target-unicore32: Mark as unmigratable
  ide/mmio: QOM'ify MMIO IDE for R2D