tests/functional: Split Aspeed ARM tests into separate files

Reorganize the monolithic Aspeed functional test files into separate
files based on firmware type (Buildroot vs SDK) and specific test
scenarios. This allows the test suite to run tests in parallel more
effectively and makes it easier to identify and run specific test
scenarios independently.

Link: https://lore.kernel.org/qemu-devel/20260209065044.239378-2-clg@redhat.com
Reviewed-by: Kane Chen <kane_chen@aspeedtech.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
8 files changed