Add an entries the Blizzard device in MAINTAINERS.

Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20190412165416.7977-6-philmd@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>