[patch] mailbox/xgene-slimpro: Checking for IS_ERR instead of NULL

[Dan Carpenter]

devm_ioremap() returns NULL, it never returns an ERR_PTR.

Fixes: f700e84f417b ('mailbox: Add support for APM X-Gene platform mailbox 
driver')
Signed-off-by: Dan Carpenter <dan.carpen...@oracle.com>

diff --git a/drivers/mailbox/mailbox-xgene-slimpro.c 
b/drivers/mailbox/mailbox-xgene-slimpro.c
index b5f5106..bd07f39 100644
--- a/drivers/mailbox/mailbox-xgene-slimpro.c
+++ b/drivers/mailbox/mailbox-xgene-slimpro.c
@@ -196,8 +196,8 @@ static int slimpro_mbox_probe(struct platform_device *pdev)
 
        regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        mb_base = devm_ioremap(&pdev->dev, regs->start, resource_size(regs));
-       if (IS_ERR(mb_base))
-               return PTR_ERR(mb_base);
+       if (!mb_base)
+               return -ENOMEM;
 
        /* Setup mailbox links */
        for (i = 0; i < MBOX_CNT; i++) {