rtc: gamecube: Fix return value check in gamecube_rtc_probe()

In case of error, the devm_kzalloc() returns NULL pointer
not ERR_PTR(). The IS_ERR() test in the return value check
should be replaced with NULL test.

Fixes: 86559400b3ef ("rtc: gamecube: Add a RTC driver for the GameCube, Wii and Wii U")
Reported-by: Hulk Robot <redacted>
Signed-off-by: Yang Yingliang <redacted>
---
 drivers/rtc/rtc-gamecube.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/rtc/rtc-gamecube.c b/drivers/rtc/rtc-gamecube.c
index 98128746171e..f717b36f4738 100644
--- a/drivers/rtc/rtc-gamecube.c
+++ b/drivers/rtc/rtc-gamecube.c

@@ -319,8 +319,8 @@ static int gamecube_rtc_probe(struct platform_device *pdev)
 	int ret;
 
 	d = devm_kzalloc(dev, sizeof(struct priv), GFP_KERNEL);
-	if (IS_ERR(d))
-		return PTR_ERR(d);
+	if (!d)
+		return -ENOMEM;
 
 	d->iob = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(d->iob))

-- 
2.25.1