drm/i915: Set MI_INVALIDATE_BSD for all video-decode engines

We have multiple instances of VCS but only remember to invalidate the
BSD caches on the first, ignoring the stale caches of any other engine.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181108140039.12254-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_lrc.c

@@ -1956,7 +1956,7 @@ static int gen8_emit_flush(struct i915_request *request, u32 mode)
 
 	if (mode & EMIT_INVALIDATE) {
 		cmd |= MI_INVALIDATE_TLB;
-		if (request->engine->id == VCS)
+		if (request->engine->class == VIDEO_DECODE_CLASS)
 			cmd |= MI_INVALIDATE_BSD;
 	}