Restore "lib: Open debugfs files for the given DRM device"

This reverts commit 25fbae15262cf570e207e62f50e7c5233e06bc67, restoring
commit 301ad44cdf1b868b1ab89096721da91fa8541fdc
Author: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Date:   Thu Mar 2 10:37:11 2017 +0100

    lib: Open debugfs files for the given DRM device

with fixes.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
73 files changed