Revert "drm/i915: Prevent module unload to avoid random memory corruption"

This reverts commit 6939a5aca7cfada279a24c307e772f33104fca20.

Daniel Vetter supplied a set of fixes for all the module unload bugs he
could trigger on his machines, so let the fun recommence!

drivers/gpu/drm/i915/i915_dma.c

@@ -2065,9 +2065,6 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 	dev_priv->mchdev_lock = &mchdev_lock;
 	spin_unlock(&mchdev_lock);
 
-	/* XXX Prevent module unload due to memory corruption bugs. */
-	__module_get(THIS_MODULE);
-
 	return 0;
 
 out_workqueue_free: