test/functional: Update buildroot images to 2024.11

test/functional: Update buildroot images to 2024.11

The main changes compared to upstream 2024.11 buildroot are

- bumped Linux to version 6.11.11 with a custom config
- changed U-Boot to OpenBMC branch for more support
- included extra target packages

See branch [1] for more details.

There is a slight output change when powering off the machine,
the console now contains :

    reboot: Power off not available: System halted

Adjust accordingly the expect string in
do_test_arm_aspeed_buildroot_poweroff().

[1] https://github.com/legoater/buildroot/commits/aspeed-2024.11

Reviewed-by: Jamin Lin <jamin_lin@aspeedtech.com>
Link: https://lore.kernel.org/qemu-devel/20250122070909.1138598-9-clg@redhat.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>