tests/qtest: Restrict bcm2835-dma-test to CONFIG_RASPI

tests/qtest: Restrict bcm2835-dma-test to CONFIG_RASPI

We will soon enable the build without TCG, which does not support many
machines, so only run the bcm2835-dma-test when the corresponding
machine is present.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
Message-Id: <20230113140419.4013-23-farosas@suse.de>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>