Input: ad7879 - return plain error code from ad7879_probe()

With the switch to devm, there is no need for ad7879_probe() to return the
touchscreen structure, we can use plain error code. This also fixes issue
introduced with devm concersion, where we returned 0 on success (which
worked OK since IS_ERR(0) would not trigger, but was not correct
regardless).

Fixes: 381f688eee3d ("Input: ad7879 - use more devm interfaces")
Acked-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
diff --git a/drivers/input/touchscreen/ad7879-spi.c b/drivers/input/touchscreen/ad7879-spi.c
index 59486cc..3457a56 100644
--- a/drivers/input/touchscreen/ad7879-spi.c
+++ b/drivers/input/touchscreen/ad7879-spi.c
@@ -32,7 +32,6 @@ static const struct regmap_config ad7879_spi_regmap_config = {
 
 static int ad7879_spi_probe(struct spi_device *spi)
 {
-	struct ad7879 *ts;
 	struct regmap *regmap;
 
 	/* don't exceed max specified SPI CLK frequency */
@@ -45,11 +44,7 @@ static int ad7879_spi_probe(struct spi_device *spi)
 	if (IS_ERR(regmap))
 		return PTR_ERR(regmap);
 
-	ts = ad7879_probe(&spi->dev, regmap, spi->irq, BUS_SPI, AD7879_DEVID);
-	if (IS_ERR(ts))
-		return PTR_ERR(ts);
-
-	return 0;
+	return ad7879_probe(&spi->dev, regmap, spi->irq, BUS_SPI, AD7879_DEVID);
 }
 
 #ifdef CONFIG_OF