drm/i915/pmu: Initialise our dynamic sysfs attributes for use with lockdep

As we kmalloc our dynamic sysfs attributes, we have to give them an
external static lock_class_key for them to use with lockdep.

Fixes: 109ec558370f ("drm/i915/pmu: Only enumerate available counters in sysfs")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180111140402.3984-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_pmu.c

@@ -719,6 +719,7 @@ static const struct attribute_group *i915_pmu_attr_groups[] = {
 static struct i915_ext_attribute *
 add_i915_attr(struct i915_ext_attribute *attr, const char *name, u64 config)
 {
+	sysfs_attr_init(&attr->attr.attr);
 	attr->attr.attr.name = name;
 	attr->attr.attr.mode = 0444;
 	attr->attr.show = i915_pmu_event_show;
@@ -731,6 +732,7 @@ static struct perf_pmu_events_attr *
 add_pmu_attr(struct perf_pmu_events_attr *attr, const char *name,
 	     const char *str)
 {
+	sysfs_attr_init(&attr->attr.attr);
 	attr->attr.attr.name = name;
 	attr->attr.attr.mode = 0444;
 	attr->attr.show = perf_event_sysfs_show;