drm: Implement dummies for debugfs helpers

In case where debugfs support is disabled, define dummy functions to
avoid the need for #ifdefery in drivers.

Based on an earlier patch by Arnd Bergmann.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
1 file changed