i386/cpu: Add x-vendor-cpuid-only-v2 option for compatibility

i386/cpu: Add x-vendor-cpuid-only-v2 option for compatibility

Add a compat property "x-vendor-cpuid-only-v2" (for PC machine v10.0
and older) to keep the original behavior. This property will be used
to adjust vendor specific CPUID fields.

Make x-vendor-cpuid-only-v2 depend on x-vendor-cpuid-only. Although
x-vendor-cpuid-only and v2 should be initernal only, QEMU doesn't
support "internal" property. To avoid any other unexpected issues, check
the dependency.

Tested-by: Yi Lai <yi1.lai@intel.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20250711102143.1622339-8-zhao1.liu@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>