powerpc/windfarm: Fix crash on SMU based machine after i2c conversion

We no longer get the device node in platform_data but instead
where it belongs in struct device, so get it from there instead
of blowing up.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

drivers/macintosh/windfarm_smu_sat.c

@@ -204,7 +204,7 @@ static struct wf_sensor_ops wf_sat_ops = {
 static int wf_sat_probe(struct i2c_client *client,
 			const struct i2c_device_id *id)
 {
-	struct device_node *dev = client->dev.platform_data;
+	struct device_node *dev = client->dev.of_node;
 	struct wf_sat *sat;
 	struct wf_sat_sensor *sens;
 	const u32 *reg;