iio: magnetometer: ak8974: Silence deferred-probe error

It's not uncommon that voltage regulator becomes available later during
kernel's boot process. This patch adds info message about unavailable
regulators in a case of the deferred-probe error and also amends the
error message with a error code.
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/magnetometer/ak8974.c

@@ -746,7 +746,12 @@ static int ak8974_probe(struct i2c_client *i2c,
 				      ARRAY_SIZE(ak8974->regs),
 				      ak8974->regs);
 	if (ret < 0) {
-		dev_err(&i2c->dev, "cannot get regulators\n");
+		if (ret != -EPROBE_DEFER)
+			dev_err(&i2c->dev, "cannot get regulators: %d\n", ret);
+		else
+			dev_dbg(&i2c->dev,
+				"regulators unavailable, deferring probe\n");
+
 		return ret;
 	}