pc: Use default_machine_opts to set suppress_vmdesc

Instead of setting suppress_vmdesc at instance_init time, set
default_machine_opts on pc_i440fx_2_2_machine_options() to
implement equivalent behavior.

This will let us eliminate the need for pc_compat_*() functions
for PC machine-types.
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>
Message-Id: <20181205205827.19387-6-ehabkost@redhat.com>
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>

hw/i386/pc_piix.c

@@ -321,7 +321,6 @@ static void pc_compat_2_3(MachineState *machine)
 static void pc_compat_2_2(MachineState *machine)
 {
     pc_compat_2_3(machine);
-    machine->suppress_vmdesc = true;
 }
 
 static void pc_compat_2_1(MachineState *machine)
@@ -572,6 +571,7 @@ static void pc_i440fx_2_2_machine_options(MachineClass *m)
     PCMachineClass *pcmc = PC_MACHINE_CLASS(m);
     pc_i440fx_2_3_machine_options(m);
     m->hw_version = "2.2.0";
+    m->default_machine_opts = "firmware=bios-256k.bin,suppress-vmdesc=on";
     SET_MACHINE_COMPAT(m, PC_COMPAT_2_2);
     pcmc->rsdp_in_ram = false;
 }