The v7-M core is specific to the Aspeed 10x0 series,
remove it from the common AspeedSoCState.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Cédric Le Goater <clg@kaod.org>