regulator: slg51000: Fix a couple NULL vs IS_ERR() checks

The devm_gpiod_get_from_of_node() function never returns NULL, it
returns error pointers on error.

Fixes: a867bde ("regulator: slg51000: add slg51000 regulator driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20190808103335.GD30506@mwanda
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: Dan Carpenter

drivers/regulator/slg51000-regulator.c

@@ -205,7 +205,7 @@ static int slg51000_of_parse_cb(struct device_node *np,
 	ena_gpiod = devm_gpiod_get_from_of_node(chip->dev, np,
 						"enable-gpios", 0,
 						gflags, "gpio-en-ldo");
-	if (ena_gpiod) {
+	if (!IS_ERR(ena_gpiod)) {
 		config->ena_gpiod = ena_gpiod;
 		devm_gpiod_unhinge(chip->dev, config->ena_gpiod);
 	}
@@ -459,7 +459,7 @@ static int slg51000_i2c_probe(struct i2c_client *client,
 					       GPIOD_OUT_HIGH
 					       | GPIOD_FLAGS_BIT_NONEXCLUSIVE,
 					       "slg51000-cs");
-	if (cs_gpiod) {
+	if (!IS_ERR(cs_gpiod)) {
 		dev_info(dev, "Found chip selector property\n");
 		chip->cs_gpiod = cs_gpiod;
 	}