chardev/baum: Use definitions to avoid dynamic stack allocation

chardev/baum: Use definitions to avoid dynamic stack allocation

We know 'x * y' will be at most 'X_MAX * Y_MAX' (which is not
a big value, it is actually 84). Instead of having the compiler
use variable-length array, declare an array able to hold the
maximum 'x * y'.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20220819153931.3147384-3-peter.maydell@linaro.org