drm/i915: Unifying debugfs return codes for unsupported features

drm/i915: Unifying debugfs return codes for unsupported features

Instead of trying different seq_puts messages, lets use common
-ENODEV error code to indicate missing/unsupported feature.

v2: don't forget about guc_log_control fops (Sagar)

Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Cc: Sujaritha Sundaresan <sujaritha.sundaresan@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171215143635.17884-1-michal.wajdeczko@intel.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>