drm/i915: Make __engine_unpark() compatible with ww locking.

Take the ww lock around engine_unpark. Because of the
many many places where rpm is used, I chose the safest option
and used a trylock to opportunistically take this lock for
__engine_unpark.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210323155059.628690-28-maarten.lankhorst@linux.intel.com

drivers/gpu/drm/i915/gt/intel_engine_pm.c

@@ -27,12 +27,16 @@ static void dbg_poison_ce(struct intel_context *ce)
 		int type = i915_coherent_map_type(ce->engine->i915);
 		void *map;
 
+		if (!i915_gem_object_trylock(obj))
+			return;
+
 		map = i915_gem_object_pin_map(obj, type);
 		if (!IS_ERR(map)) {
 			memset(map, CONTEXT_REDZONE, obj->base.size);
 			i915_gem_object_flush_map(obj);
 			i915_gem_object_unpin_map(obj);
 		}
+		i915_gem_object_unlock(obj);
 	}
 }