Path check was done on /dev/dri/card and /dev/dri/renderD. However,
/dev/dri/by-path is a thing, and on FreeBSD, /dev/dri/ symlinks to
/dev/drm/.
Relax Linux check to /dev/dri/, and add FreeBSD check for /dev/drm/.
FreeBSD device numbers cannot be used to check the type of a device, as
they are merely unique filesystem IDs.
As the paths we use have been sanitized with realpath, we can simply use
the path to check if a requested file is an evdev or drm device. This
also allows us to make the check before the file is opened.
