target.json: add a note about query-cpu* not being s390x-specific

Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Acked-by: NCornelia Huck <cohuck@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Message-Id: <20190214152251.2073-12-armbru@redhat.com>

qapi/target.json

@@ -275,6 +275,9 @@
 #          an unknown cpu definition name, unknown properties or properties
 #          with wrong types.
 #
+# Note: this command isn't specific to s390x, but is only implemented
+# on this architecture currently.
+#
 # Since: 2.8.0
 ##
 { 'command': 'query-cpu-model-comparison',
@@ -315,6 +318,9 @@
 #          an unknown cpu definition name, unknown properties or properties
 #          with wrong types.
 #
+# Note: this command isn't specific to s390x, but is only implemented
+# on this architecture currently.
+#
 # Since: 2.8.0
 ##
 { 'command': 'query-cpu-model-baseline',