memory: stm32_omm: Fix NULL vs IS_ERR() check in probe()

The platform_get_resource_byname() function returns NULL on error.  It
doesn't return error pointers.  Update the check to match.

Fixes: 8181d06 ("memory: Add STM32 Octo Memory Manager driver")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/a1645f1eedaa9b2ae62ac07feed0552eea75bc46.1746781081.git.dan.carpenter@linaro.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Author: Dan Carpenter

drivers/memory/stm32_omm.c

@@ -320,8 +320,8 @@ static int stm32_omm_probe(struct platform_device *pdev)
 		return PTR_ERR(omm->io_base);
 
 	omm->mm_res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "memory_map");
-	if (IS_ERR(omm->mm_res))
-		return PTR_ERR(omm->mm_res);
+	if (!omm->mm_res)
+		return -ENODEV;
 
 	/* check child's access */
 	for_each_child_of_node_scoped(dev->of_node, child) {