cpu: Remove the verification conditions of the model in the x86 signatures

The x86ModelParseSignatures function makes an assumption that CPU signature
model equals 0 as an invalid case. While in Hygon processor definition, A1
version (model 0, stepping 1) is mass production version, to support Hygon
Dhyana A1 version, we have removed CPU signature model zero checking condition.
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>
Signed-off-by: NYingle Hou <houyingle@hygon.cn>

src/cpu/cpu_x86.c

@@ -1418,7 +1418,7 @@ x86ModelParseSignatures(virCPUx86ModelPtr model,
         }
 
         rc = virXPathUInt("string(@model)", ctxt, &sigModel);
-        if (rc < 0 || sigModel == 0) {
+        if (rc < 0) {
             virReportError(VIR_ERR_INTERNAL_ERROR,
                            _("Invalid CPU signature model in model %s"),
                            model->name);