remoteproc: mediatek: Refactor single core check and fix retrocompatibility

In older devicetrees we had the ChromeOS EC in a node called "cros-ec"
instead of the newer "cros-ec-rpmsg", but this driver is now checking
only for the latter, breaking compatibility with those.

Besides, we can check if the SCP is single or dual core by simply
walking through the children of the main SCP node and checking if
if there's more than one "mediatek,scp-core" compatible node.

Fixes: 1fdbf0cd ("remoteproc: mediatek: Probe SCP cluster on multi-core SCP")
Reported-by: "kernelci.org bot" <bot@kernelci.org>
Tested-by: Laura Nao <laura.nao@collabora.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20230919092336.51007-1-angelogioacchino.delregno@collabora.comSigned-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

drivers/remoteproc/mtk_scp.c

@@ -1144,29 +1144,25 @@ static int scp_add_multi_core(struct platform_device *pdev,
 	return ret;
 }
 
-static int scp_is_single_core(struct platform_device *pdev)
+static bool scp_is_single_core(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct device_node *np = dev_of_node(dev);
 	struct device_node *child;
+	int num_cores = 0;
 
-	child = of_get_next_available_child(np, NULL);
-	if (!child)
-		return dev_err_probe(dev, -ENODEV, "No child node\n");
+	for_each_child_of_node(np, child)
+		if (of_device_is_compatible(child, "mediatek,scp-core"))
+			num_cores++;
 
-	of_node_put(child);
-	return of_node_name_eq(child, "cros-ec-rpmsg");
+	return num_cores < 2;
 }
 
 static int scp_cluster_init(struct platform_device *pdev, struct mtk_scp_of_cluster *scp_cluster)
 {
 	int ret;
 
-	ret = scp_is_single_core(pdev);
-	if (ret < 0)
-		return ret;
-
-	if (ret)
+	if (scp_is_single_core(pdev))
 		ret = scp_add_single_core(pdev, scp_cluster);
 	else
 		ret = scp_add_multi_core(pdev, scp_cluster);