tests/qtest: Migrate GMAC test from 7xx to 8xx

tests/qtest: Migrate GMAC test from 7xx to 8xx

For upstreaming we migrated this test to 7xx (since that was already
upstream) move it back to 8xx where it can check the 4 GMACs since that
is the board this test was originally created for.

Signed-off-by: Nabih Estefan <nabihestefan@google.com>
Message-id: 20250508220718.735415-3-nabihestefan@google.com
Reviewed-by: Tyrone Ting <kfting@nuvoton.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>