iio: dac: stm32-dac: Use pm_runtime_resume_and_get() to replace open coding.

Found using coccicheck script under review at:
https://lore.kernel.org/lkml/20210427141946.2478411-1-Julia.Lawall@inria.fr/

This is a prequel to taking a closer look at the runtime pm in IIO drivers
in general
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Reviewed-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/20210509113354.660190-17-jic23@kernel.org

drivers/iio/dac/stm32-dac.c

@@ -69,9 +69,8 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
 	}
 
 	if (enable) {
-		ret = pm_runtime_get_sync(dev);
+		ret = pm_runtime_resume_and_get(dev);
 		if (ret < 0) {
-			pm_runtime_put_noidle(dev);
 			mutex_unlock(&dac->lock);
 			return ret;
 		}