spi: Fix regression to return zero on success instead of positive value

Commit d948e6ca ("spi: add power control when set_cs") added generic
runtime PM handling, but also changed the return value to be 1 instead
of 0 that we had earlier as pm_runtime_get functions return a positve
value on success.

This causes SPI devices to return errors for cases where they do:

ret = spi_setup(spi);
if (ret)
	return ret;

As in many cases the SPI devices do not check for if (ret < 0).

Let's fix this by setting the status to 0 on succeess after the
runtime PM calls. Let's not return 0 at the end of the function
as this might break again later on if the function changes and
starts returning status again.

Fixes: d948e6ca ("spi: add power control when set_cs")
Cc: Luhua Xu <luhua.xu@mediatek.com>
Cc: wsd_upstream@mediatek.com
Signed-off-by: Tony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/20191111195334.44833-1-tony@atomide.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi.c

@@ -3269,6 +3269,15 @@ int spi_setup(struct spi_device *spi)
 				status);
 			return status;
 		}
+
+		/*
+		 * We do not want to return positive value from pm_runtime_get,
+		 * there are many instances of devices calling spi_setup() and
+		 * checking for a non-zero return value instead of a negative
+		 * return value.
+		 */
+		status = 0;
+
 		spi_set_cs(spi, false);
 		pm_runtime_mark_last_busy(spi->controller->dev.parent);
 		pm_runtime_put_autosuspend(spi->controller->dev.parent);