x86_cpu_flags:new case to test amd flags

Signed-off-by: NNana Liu <nanliu@redhat.com>

qemu/tests/cfg/x86_cpu_flags.cfg

@@ -19,3 +19,11 @@
                     no RHEL.6 RHEL.7 RHEL.8.0 RHEL.8.1
                     cpu_model_flags += ",+avx512-bf16"
                     flags = "avx512_bf16"
+        - amd:
+            vendor_id = 'amd'
+            variants:
+                - flag_1:
+                    # support RHEL.7 guest or later
+                    no RHEL.6
+                    cpu_model_flags += ",+xsaveerptr,+clzero"
+                    flags = "clzero xsaveerptr"