iio: magnetometer: ak8974: mark INT_CLEAR as precious

Reading INT_CLEAR has side effects - disallow reading it via debugfs.
Signed-off-by: NMichał Mirosław <mirq-linux@rere.qmqm.pl>
Reviewed-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NJonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/magnetometer/ak8974.c

@@ -661,11 +661,17 @@ static bool ak8974_writeable_reg(struct device *dev, unsigned int reg)
 	}
 }
 
+static bool ak8974_precious_reg(struct device *dev, unsigned int reg)
+{
+	return reg == AK8974_INT_CLEAR;
+}
+
 static const struct regmap_config ak8974_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
 	.max_register = 0xff,
 	.writeable_reg = ak8974_writeable_reg,
+	.precious_reg = ak8974_precious_reg,
 };
 
 static int ak8974_probe(struct i2c_client *i2c,