i386/cpu: Enable 0x1f leaf for YongFeng by default

Host YongFeng CPU has 0x1f leaf by default, so that enable it for
Guest CPU by default as well.

Suggested-by: Ewan Hai <ewanhai-oc@zhaoxin.com>
Tested-by: Yi Lai <yi1.lai@intel.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20250711104603.1634832-10-zhao1.liu@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

target/i386/cpu.c

@@ -6548,8 +6548,12 @@ static const X86CPUDefinition builtin_x86_defs[] = {
             },
             {
                 .version = 3,
-                .note = "with the cache model",
+                .note = "with the cache model and 0x1f leaf",
                 .cache_info = &yongfeng_cache_info,
+                .props = (PropValue[]) {
+                    { "x-force-cpuid-0x1f", "on" },
+                    { /* end of list */ },
+                }
             },
             { /* end of list */ }
         }