ASoc: wm8731: Drop empty spi_driver remove callback

A driver with a remove callback that just returns 0 behaves identically
to a driver with no remove callback at all. So simplify accordingly.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20211020125803.23117-1-u.kleine-koenig@pengutronix.deSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/wm8731.c

@@ -713,18 +713,12 @@ static int wm8731_spi_probe(struct spi_device *spi)
 	return 0;
 }
 
-static int wm8731_spi_remove(struct spi_device *spi)
-{
-	return 0;
-}
-
 static struct spi_driver wm8731_spi_driver = {
 	.driver = {
 		.name	= "wm8731",
 		.of_match_table = wm8731_of_match,
 	},
 	.probe		= wm8731_spi_probe,
-	.remove		= wm8731_spi_remove,
 };
 #endif /* CONFIG_SPI_MASTER */