powerpc/iseries: use DECLARE_COMPLETION_ONSTACK for non-constant completion

The _ONSTACK variant should be used for on-stack completion,
otherwise it will break lockdep.

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: linuxppc-dev@ozlabs.org
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/iseries/viopath.c

@@ -116,7 +116,7 @@ static int proc_viopath_show(struct seq_file *m, void *v)
 	u16 vlanMap;
 	dma_addr_t handle;
 	HvLpEvent_Rc hvrc;
-	DECLARE_COMPLETION(done);
+	DECLARE_COMPLETION_ONSTACK(done);
 	struct device_node *node;
 	const char *sysid;