gitlab-ci: Restrict s390x/ppc64el jobs to packet runners

They are hitting timeouts on the gstreamer runners now... *sigh*

Reviewed-by: Adam Jackson <ajax@redhat.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4233>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4233>
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index fbe88ed..7309414 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -487,6 +487,8 @@
 meson-s390x:
   extends:
     - .meson-cross
+  tags:
+    - kvm
   variables:
     CROSS: s390x
     GALLIUM_DRIVERS: "swrast"