drm/nv84: fix minor issues in PCRYPT implementation

Fix running of destroy_context() when create_context() has never been
called for the channel, and fill in engine's tlb_flush() function pointer.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_state.c

@@ -437,6 +437,7 @@ static int nouveau_init_engine_ptrs(struct drm_device *dev)
 			engine->crypt.takedown	= nv84_crypt_fini;
 			engine->crypt.create_context = nv84_crypt_create_context;
 			engine->crypt.destroy_context = nv84_crypt_destroy_context;
+			engine->crypt.tlb_flush	= nv84_crypt_tlb_flush;
 			break;
 		default:
 			engine->crypt.init	= nouveau_stub_init;

drivers/gpu/drm/nouveau/nv84_crypt.c

@@ -61,7 +61,7 @@ nv84_crypt_destroy_context(struct nouveau_channel *chan)
 	struct drm_device *dev = chan->dev;
 	u32 inst;
 
-	if (!chan->ramin)
+	if (!chan->crypt_ctx)
 		return;
 
 	inst  = (chan->ramin->vinst >> 12);