hw/loongarch/virt: Fix memory leak

hw/loongarch/virt: Fix memory leak

The char pointer 'ramName' point to a block of memory,
but never free it. Use 'g_autofree' to automatically free it.

Resolves: Coverity CID 1544773

Fixes: 0cf1478d6 ("hw/loongarch: Add numa support")
Signed-off-by: Song Gao <gaosong@loongson.cn>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20240507022239.3113987-1-gaosong@loongson.cn>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>