spi: spi-nxp-fspi: Fix a NULL vs IS_ERR() check in probe

The platform_get_resource_byname() function returns NULL on error, it
doesn't return error pointers.

Fixes: d166a735 ("spi: fspi: dynamically alloc AHB memory")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20200312113154.GC20562@mwandaSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-nxp-fspi.c

@@ -1019,8 +1019,8 @@ static int nxp_fspi_probe(struct platform_device *pdev)
 
 	/* find the resources - controller memory mapped space */
 	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "fspi_mmap");
-	if (IS_ERR(res)) {
-		ret = PTR_ERR(res);
+	if (!res) {
+		ret = -ENODEV;
 		goto err_put_ctrl;
 	}