soc: fsl: guts: fix return value check in fsl_guts_init()

In case of error, of_iomap() returns NULL pointer not ERR_PTR().
The IS_ERR() test in the return value check should be replaced
with NULL test and return -ENOMEM as error value.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Michael Walle <michael@walle.cc>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

drivers/soc/fsl/guts.c

@@ -195,9 +195,9 @@ static int __init fsl_guts_init(void)
 	soc_data = match->data;
 
 	regs = of_iomap(np, 0);
-	if (IS_ERR(regs)) {
+	if (!regs) {
 		of_node_put(np);
-		return PTR_ERR(regs);
+		return -ENOMEM;
 	}
 
 	little_endian = of_property_read_bool(np, "little-endian");