drm/i915: Suppress no action noise from oom shrinker

If we are not able to free anything (the shrinker leaves nothing on the
global object lists), do not log anything. This is useful when other
subsystems are being stress-tested for their oom behaviour and i915.ko
is shouting into the logs about doing nothing.
Reported-by: NDave Jones <davej@redhat.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem.c

@@ -5307,8 +5307,9 @@ i915_gem_shrinker_oom(struct notifier_block *nb, unsigned long event, void *ptr)
 	if (unlock)
 		mutex_unlock(&dev->struct_mutex);
 
-	pr_info("Purging GPU memory, %lu bytes freed, %lu bytes still pinned.\n",
-		freed_pages << PAGE_SHIFT, pinned);
+	if (freed_pages || unbound || bound)
+		pr_info("Purging GPU memory, %lu bytes freed, %lu bytes still pinned.\n",
+			freed_pages << PAGE_SHIFT, pinned);
 	if (unbound || bound)
 		pr_err("%lu and %lu bytes still available in the "
 		       "bound and unbound GPU page lists.\n",