Add DRMFILE definitions and supply filp for BSD in the

    post-drm-filp-0-1-branch world. The filp is a void * cast from the
    current pid. This is a temporary solution which maintains the status
    quo until a proper solution is implemented.
What is really needed is a unique pointer per open, hopefully with a device
    private area. This can be done in FreeBSD for all entry points except
    mmap, but is difficult (sys/dev/streams/streams.c is an example). I
    have partially completed code for this but have not had time to debug,
    so this is a temporary fix.