hw/net: Have eTSEC device inherit from DYNAMIC_SYS_BUS_DEVICE

hw/net: Have eTSEC device inherit from DYNAMIC_SYS_BUS_DEVICE

Because the network eTSEC device can be optionally plugged on the
TYPE_PLATFORM_BUS_DEVICE, have it inherit TYPE_DYNAMIC_SYS_BUS_DEVICE.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alexander Graf <graf@amazon.com>
Reviewed-by: Clément Mathieu--Drif <clement.mathieu--drif@eviden.com>
Tested-by: Bernhard Beschow <shentey@gmail.com>
Acked-by: Bernhard Beschow <shentey@gmail.com>
Message-Id: <20250125181343.59151-8-philmd@linaro.org>