[PATCH -next] n64: fix return value check in n64cart_probe()

In case of error, the function devm_platform_ioremap_resource()
returns ERR_PTR() and never returns NULL. The NULL test in the
return value check should be replaced with IS_ERR().

Fixes: d9b2a2bbbb4d ("block: Add n64 cart driver")
Reported-by: Hulk Robot <redacted>
Signed-off-by: Wei Yongjun <redacted>
---
 drivers/block/n64cart.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/block/n64cart.c b/drivers/block/n64cart.c
index 47bdf324e962..84a0f8d0be29 100644
--- a/drivers/block/n64cart.c
+++ b/drivers/block/n64cart.c

@@ -129,8 +129,8 @@ static int __init n64cart_probe(struct platform_device *pdev)
 	}
 
 	reg_base = devm_platform_ioremap_resource(pdev, 0);
-	if (!reg_base)
-		return -EINVAL;
+	if (IS_ERR(reg_base))
+		return ERR_PTR(reg_base);
 
 	disk = alloc_disk(0);
 	if (!disk)