pc: Define MACHINE_OPTIONS macros consistently for all machines

pc: Define MACHINE_OPTIONS macros consistently for all machines

Define a MACHINE_OPTIONS macro for each PC machine, and move every field
inside the QEMUMachine structs to the macros, except for name, init, and
compat_props.

This also ensures that all MACHINE_OPTIONS inherit the fields from the
next version, so their definitions carry only the changes that exist
between one version and the next one.

Comments about specific cases:

pc-*-2.1:

  Existing PC_*_2_1_MACHINE_OPTIONS macros were defined as:
      PC_*_MACHINE_OPTIONS,
      .default_machine_opts = "firmware=bios-256k.bin"

  PC_*_2_2_MACHINE_OPTIONS is:
      PC_*_2_3_MACHINE_OPTIONS
  which is expanded to:
      PC_*_MACHINE_OPTIONS,
      .default_machine_opts = "firmware=bios-256k.bin",
      .default_display = "std"

  The only difference between 2_1 and 2_2 is .default_display, that's why
  we didn't reuse PC_*_2_2_MACHINE_OPTIONS. The good news is that having
  multiple initializers for a field is allowed by C99, and the last
  initializer overrides the previous ones.

  So we can reuse the 2_2 macro in 2_1 and define PC_*_2_1_MACHINE_OPTIONS
  as:
      PC_*_2_2_MACHINE_OPTIONS,
      .default_display = NULL

pc-*-1.7:

  PC_*_1_7_MACHINE_OPTIONS was defined as:
      PC_*_MACHINE_OPTIONS

  PC_*_2_0_MACHINE_OPTIONS is defined as:
      PC_*_2_1_MACHINE_OPTIONS
  which is expanded to:
      PC_*_2_2_MACHINE_OPTIONS,
      .default_display = NULL
  which is expanded to:
      PC_*_2_3_MACHINE_OPTIONS,
      .default_display = NULL
  which is expanded to:
      PC_*_MACHINE_OPTIONS,
      .default_machine_opts = "firmware=bios-256k.bin",
      .default_display = "std",
      .default_display = NULL  /* overrides the previous line */

  So, the only difference between PC_*_1_7_MACHINE_OPTIONS and
  PC_*_2_0_MACHINE_OPTIONS is .default_machine_opts (as .default_display
  is not explicitly set by PC_*_MACHINE_OPTIONS so it is NULL).

  So we can keep the macro reuse pattern and define
  PC_*_2_0_MACHINE_OPTIONS as:
      PC_*_2_0_MACHINE_OPTIONS,
      .default_machine_opts = NULL

pc-*-2.4 (alias and is_default fields):

  Set alias and is_default fields inside the 2.4 MACHINE_OPTIONS macro,
  and clear it in the 2.3 macro (that reuses the 2.4 macro).

hw_machine:

  As all the machines older than v1.0 set hw_version explicitly, we can
  safely move the field to the MACHINE_OPTIONS macros without affecting
  the other versions that reuse them.

init function:

  Some machines had the init function set inside the MACHINE_OPTIONS
  macro. Move it to the QEMUMachine declaration, to keep it consistent
  with the other machines.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>