drm/i915: Remove obsolete code from intelfb_alloc()

Clean up after 0c82312f3f15 ("drm/i915: Pin the ifbdev for the
info->system_base GGTT mmapping"):

At each of the remaining "goto out" in intelfb_alloc(), fb can only be
either an ERR_PTR or NULL, so the call to drm_framebuffer_unreference()
is now obsolete.

Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Link: http://patchwork.freedesktop.org/patch/msgid/56756c41.c306c20a.d0602.1830SMTPIN_ADDED_MISSING@mx.google.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_fbdev.c

@@ -119,7 +119,7 @@ static int intelfb_alloc(struct drm_fb_helper *helper,
 {
 	struct intel_fbdev *ifbdev =
 		container_of(helper, struct intel_fbdev, helper);
-	struct drm_framebuffer *fb = NULL;
+	struct drm_framebuffer *fb;
 	struct drm_device *dev = helper->dev;
 	struct drm_i915_private *dev_priv = to_i915(dev);
 	struct drm_mode_fb_cmd2 mode_cmd = {};
@@ -171,8 +171,6 @@ static int intelfb_alloc(struct drm_fb_helper *helper,
 
 out:
 	mutex_unlock(&dev->struct_mutex);
-	if (!IS_ERR_OR_NULL(fb))
-		drm_framebuffer_unreference(fb);
 	return ret;
 }