iio: dac: ltc1660: Switch to DEFINE_SIMPLE_DEV_PM_OPS() and pm_sleep_ptr()

Using these newer macros allows the compiler to remove the unused
structure and functions when !CONFIG_PM_SLEEP + removes the need to
mark pm functions __maybe_unused.

Signed-off-by: Jonathan Cameron <[e-mail]>
Cc: Marcus Folkesson <[e-mail]>
Reviewed-by: Marcus Folkesson <[e-mail]>
Reviewed-by: Paul Cercueil <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/iio/dac/ltc1660.c

···
 	.write_raw = &ltc1660_write_raw,
 };
 
-static int __maybe_unused ltc1660_suspend(struct device *dev)
+static int ltc1660_suspend(struct device *dev)
 {
 	struct ltc1660_priv *priv = iio_priv(spi_get_drvdata(
 						to_spi_device(dev)));
 	return regmap_write(priv->regmap, LTC1660_REG_SLEEP, 0x00);
 }
 
-static int __maybe_unused ltc1660_resume(struct device *dev)
+static int ltc1660_resume(struct device *dev)
 {
 	struct ltc1660_priv *priv = iio_priv(spi_get_drvdata(
 						to_spi_device(dev)));
 	return regmap_write(priv->regmap, LTC1660_REG_WAKE, 0x00);
 }
-static SIMPLE_DEV_PM_OPS(ltc1660_pm_ops, ltc1660_suspend, ltc1660_resume);
+static DEFINE_SIMPLE_DEV_PM_OPS(ltc1660_pm_ops, ltc1660_suspend,
+				ltc1660_resume);
 
 static int ltc1660_probe(struct spi_device *spi)
 {
···
 	.driver = {
 		.name = "ltc1660",
 		.of_match_table = ltc1660_dt_ids,
-		.pm = &ltc1660_pm_ops,
+		.pm = pm_sleep_ptr(&ltc1660_pm_ops),
 	},
 	.probe	= ltc1660_probe,
 	.remove = ltc1660_remove,