iio: dac: stm32-dac: Replace open coded str_enable_disable()

Replace open coded str_enable_disable() in error message in
stm32_dac_set_enable_state().

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220616220023.9894-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/dac/stm32-dac.c

@@ -16,6 +16,7 @@
 #include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
+#include <linux/string_helpers.h>
 
 #include "stm32-dac-core.h"
 
@@ -81,8 +82,7 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
 	ret = regmap_update_bits(dac->common->regmap, STM32_DAC_CR, msk, en);
 	mutex_unlock(&dac->lock);
 	if (ret < 0) {
-		dev_err(&indio_dev->dev, "%s failed\n", en ?
-			"Enable" : "Disable");
+		dev_err(&indio_dev->dev, "%s failed\n", str_enable_disable(en));
 		goto err_put_pm;
 	}