drm/i915: properly check for MODESET for kms driver ioctls

Also ditch the cargo-culted dev_priv checks - either we have a
giant hole in our setup code or this is useless. Plainly bogus
to check for it in either case.

v2: Chris Wilson noticed that I've missed one bogus dev_priv check.

v3: The check in the overlay code is redundant (Chris)

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index cf9dfcd..e1716be 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6189,15 +6189,12 @@
 int intel_get_pipe_from_crtc_id(struct drm_device *dev, void *data,
 				struct drm_file *file)
 {
-	drm_i915_private_t *dev_priv = dev->dev_private;
 	struct drm_i915_get_pipe_from_crtc_id *pipe_from_crtc_id = data;
 	struct drm_mode_object *drmmode_obj;
 	struct intel_crtc *crtc;
 
-	if (!dev_priv) {
-		DRM_ERROR("called with no initialization\n");
-		return -EINVAL;
-	}
+	if (!drm_core_check_feature(dev, DRIVER_MODESET))
+		return -ENODEV;
 
 	drmmode_obj = drm_mode_object_find(dev, pipe_from_crtc_id->crtc_id,
 			DRM_MODE_OBJECT_CRTC);