meson: fix module config

Use all config symbols not only the host ones.
Needed to make sure device configs like CONFIG_QXL
are used for modules too.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 20200914134224.29769-3-kraxel@redhat.com