platform/x86: pcengines-apuv2: detect apuv4 board

GPIO stuff on APUv4 seems to be the same as on APUv2, so we just
need to match on DMI data.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>