target/i386: Add support for Zhaoxin CPU vendor identification

target/i386: Add support for Zhaoxin CPU vendor identification

Zhaoxin currently uses two vendors: "Shanghai" and "Centaurhauls".
It is important to note that the latter now belongs to Zhaoxin. Therefore,
this patch replaces CPUID_VENDOR_VIA with CPUID_VENDOR_ZHAOXIN1.

The previous CPUID_VENDOR_VIA macro was only defined but never used in
QEMU, making this change straightforward.

Additionally, the IS_ZHAOXIN_CPU macro has been added to simplify the
checks for Zhaoxin CPUs.

Signed-off-by: EwanHai <ewanhai-oc@zhaoxin.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20250113074413.297793-2-ewanhai-oc@zhaoxin.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>