tests/acceptance: Test ast2400 and ast2500 machines

tests/acceptance: Test ast2400 and ast2500 machines

Test MTD images from the OpenBMC project on AST2400 and AST2500 SoCs
from ASPEED, by booting Palmetto and Romulus BMC machines.

The images are fetched from OpenBMC's release directory on github.

Cc: Cleber Rosa <crosa@redhat.com>
Cc: Wainer dos Santos Moschetta <wainersm@redhat.com>
Co-developed-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Tested-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Cleber Rosa <crosa@redhat.com>
Tested-by: Cleber Rosa <crosa@redhat.com>
[ clg : - removed comment
        - removed ending self.vm.shutdown() ]
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20210304123951.163411-2-joel@jms.id.au>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Willian Rampazzo <willianr@redhat.com>
Message-Id: <20210407171637.777743-12-clg@kaod.org>
Signed-off-by: Cédric Le Goater <clg@kaod.org>