hw/arm/sbsa-ref: Don't leak string in sbsa_fdt_add_gic_node()

In sbsa_fdt_add_gic_node() we g_strdup_printf() two nodename
strings, but only free one.

Since the string is actually entirely constant and we don't
make any use of printf's format-string operations, we can
drop the g_strdup_printf() use entirely.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Message-id: 20240822162323.706382-1-peter.maydell@linaro.org