drm/i915: stop assigning drm->dev_private pointer

We no longer need or use it as we subclass struct drm_device in our
struct drm_i915_private, and can always use to_i915() to get at
i915. Stop assigning the pointer to catch anyone trying to add new users
for ->dev_private.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Dale B Stimson <dale.b.stimson@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200224113312.13674-1-jani.nikula@intel.com

drivers/gpu/drm/i915/i915_drv.c

@@ -1375,8 +1375,6 @@ i915_driver_create(struct pci_dev *pdev, const struct pci_device_id *ent)
 		return ERR_PTR(err);
 	}
 
-	i915->drm.dev_private = i915;
-
 	i915->drm.pdev = pdev;
 	pci_set_drvdata(pdev, i915);
 

drivers/gpu/drm/i915/selftests/mock_gem_device.c

@@ -144,7 +144,6 @@ struct drm_i915_private *mock_gem_device(void)
 		goto put_device;
 	}
 	i915->drm.pdev = pdev;
-	i915->drm.dev_private = i915;
 
 	intel_runtime_pm_init_early(&i915->runtime_pm);