hw/arm/xlnx-versal-virt: rename the machine to amd-versal-virt

hw/arm/xlnx-versal-virt: rename the machine to amd-versal-virt

To align with current branding and ensure coherency with the upcoming
versal2 machine, rename the xlnx-versal-virt machine to amd-versal-virt.
Keep an alias of the old name to the new one for command-line backward
compatibility.

Signed-off-by: Luc Michel <luc.michel@amd.com>
Reviewed-by: Francisco Iglesias <francisco.iglesias@amd.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20250926070806.292065-42-luc.michel@amd.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>