drm/i915: Merge pre/postclose hooks

There's really not a reason afaics that we can't just clean up
everything at the end, in the terminal postclose hook: Since this is
closing a file descriptor we know no one else can have a reference or
a thread doing something with that drm_file except the close code.
Ordering shouldn't matter, as long as we don't kfree before we clean
stuff up.

In the past this was more relevant when drivers still had to track and
clean up pending drm events, but that's all done by the core now.

Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Liviu Dudau <Liviu.Dudau@arm.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170308141257.12119-13-daniel.vetter@ffwll.ch

drivers/gpu/drm/i915/i915_drv.c

@@ -1420,17 +1420,14 @@ static void i915_driver_lastclose(struct drm_device *dev)
 	vga_switcheroo_process_delayed_switch();
 }
 
-static void i915_driver_preclose(struct drm_device *dev, struct drm_file *file)
+static void i915_driver_postclose(struct drm_device *dev, struct drm_file *file)
 {
+	struct drm_i915_file_private *file_priv = file->driver_priv;
+
 	mutex_lock(&dev->struct_mutex);
 	i915_gem_context_close(dev, file);
 	i915_gem_release(dev, file);
 	mutex_unlock(&dev->struct_mutex);
-}
-
-static void i915_driver_postclose(struct drm_device *dev, struct drm_file *file)
-{
-	struct drm_i915_file_private *file_priv = file->driver_priv;
 
 	kfree(file_priv);
 }
@@ -2635,7 +2632,6 @@ static struct drm_driver driver = {
 	.release = i915_driver_release,
 	.open = i915_driver_open,
 	.lastclose = i915_driver_lastclose,
-	.preclose = i915_driver_preclose,
 	.postclose = i915_driver_postclose,
 	.set_busid = drm_pci_set_busid,