target/i386: Fix cpuid level for AMD

A AMD server typically has cpuid level 0x10(test on Rome/Milan), it
should not be changed to 0x1f in multi-dies case.

* to maintain compatibility with older machine types, only implement
  this change when the CPU's "x-vendor-cpuid-only" property is false

Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: zhenwei pi <pizhenwei@bytedance.com>
Fixes: a94e1428 (target/i386: Add CPUID.1F generation support for multi-dies PCMachine)
Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Message-Id: <20210708170641.49410-1-michael.roth@amd.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>