Creating 1GB image for a simple qtest is unnecessary
and could lead to failures. We reduce the image size
to 1MB to reduce the test overhead.

Signed-off-by: Hao Wu <wuhaotsh@google.com>
Message-id: 20220609214125.4192212-1-wuhaotsh@google.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>