tests/avocado/machine_aspeed.py: update buildroot tests

tests/avocado/machine_aspeed.py: update buildroot tests

Use buildroot 2022.11 based images plus some customization :

  - Linux version is bumped to 6.0.9 and kernel is built with a custom
    config similar to what OpenBMC provides.
  - U-Boot is switched to the one provided by OpenBMC for better support.
  - defconfigs includes more target tools for dev.

Reviewed-by: Joel Stanley <joel@jms.id.au>
Message-Id: <20230119123449.531826-7-clg@kaod.org>
Signed-off-by: Cédric Le Goater <clg@kaod.org>