mesa: Fix detection of invalidating both depth and stencil.

mesa: Fix detection of invalidating both depth and stencil.

Fixes an extra 1024x1024x4 MSAA Z/S store on WebGL fishtank on cheza.

Reported-by: Dave Airlie <airlied@redhat.com>
Fixes: db2ae5112106 ("mesa: Skip partial InvalidateFramebuffer of packed depth/stencil.")
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Reviewed-by: Rob Clark <robdclark@chromium.org>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3370>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3370>