iio: tsl4531: Fix compiler error when CONFIG_PM_OPS is not defined

Fix the compiler error when the CONFIG_PM_OPS flag is not set.

drivers/iio/light/tsl4531.c:235:8: error: ‘tsl4531_suspend’ undeclared here (not in a function)
drivers/iio/light/tsl4531.c:235:8: error: ‘tsl4531_resume’ undeclared here (not in a function)

Signed-off-by: Dan Murphy <dmurphy@ti.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/light/tsl4531.c

@@ -230,9 +230,12 @@ static int tsl4531_resume(struct device *dev)
 	return i2c_smbus_write_byte_data(to_i2c_client(dev), TSL4531_CONTROL,
 		TSL4531_MODE_NORMAL);
 }
-#endif
 
 static SIMPLE_DEV_PM_OPS(tsl4531_pm_ops, tsl4531_suspend, tsl4531_resume);
+#define TSL4531_PM_OPS (&tsl4531_pm_ops)
+#else
+#define TSL4531_PM_OPS NULL
+#endif
 
 static const struct i2c_device_id tsl4531_id[] = {
 	{ "tsl4531", 0 },
@@ -243,7 +246,7 @@ MODULE_DEVICE_TABLE(i2c, tsl4531_id);
 static struct i2c_driver tsl4531_driver = {
 	.driver = {
 		.name   = TSL4531_DRV_NAME,
-		.pm	= &tsl4531_pm_ops,
+		.pm	= TSL4531_PM_OPS,
 		.owner  = THIS_MODULE,
 	},
 	.probe  = tsl4531_probe,