hw/xfree86: Propagate physical dimensions from DRM connector

Physical dimmension of display can be obtained not just by configuration or
DDC, but also directly from kernel via drmModeGetConnector(). Until now
xserver silently discarded these values even when no configuration nor EDID
were present and fallbacked to default DPI.
5 jobs for drmdimensionsfix in 8 minutes and 35 seconds (queued for 3 seconds)