regulator: cros-ec-regulator: Add NULL test for devm_kmemdup call

Fix possible NULL pointer dereference.
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Link: https://lore.kernel.org/r/20200802032509.305425-1-axel.lin@ingics.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/cros-ec-regulator.c

@@ -170,6 +170,9 @@ static int cros_ec_regulator_init_info(struct device *dev,
 	data->voltages_mV =
 		devm_kmemdup(dev, resp.voltages_mv,
 			     sizeof(u16) * data->num_voltages, GFP_KERNEL);
+	if (!data->voltages_mV)
+		return -ENOMEM;
+
 	data->desc.n_voltages = data->num_voltages;
 
 	/* Make sure the returned name is always a valid string */