target-i386: Change CPUID model of 486 to 8

This changes the model number of 486 to 8 (DX4) which matches the
feature set presented, and actually has the CPUID instruction.

This adds a compatibility property, to keep model=0 on pc-*-1.4 and older.
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
[AF: Add compat_props entry]
Tested-by: NEduardo Habkost <ehabkost@redhat.com>
Reviewed-by: NEduardo Habkost <ehabkost@redhat.com>
Signed-off-by: NAndreas Färber <afaerber@suse.de>

include/hw/i386/pc.h

@@ -242,6 +242,10 @@ int e820_add_entry(uint64_t, uint64_t, uint32_t);
             .driver   = "pc-sysfw",\
             .property = "rom_only",\
             .value    = stringify(0),\
+        },{\
+            .driver   = "486-" TYPE_X86_CPU,\
+            .property = "model",\
+            .value    = stringify(0),\
         }
 
 #endif

target-i386/cpu.c

@@ -588,7 +588,7 @@ static x86_def_t builtin_x86_defs[] = {
         .level = 1,
         .vendor = CPUID_VENDOR_INTEL,
         .family = 4,
-        .model = 0,
+        .model = 8,
         .stepping = 0,
         .features[FEAT_1_EDX] =
             I486_FEATURES,