soc: ux500: Use custom soc attribute group instead of device_create_file

Commit c31e7312 ("base: soc: Handle custom soc information sysfs
entries") introduced custom soc attribute group in soc_device_attribute
structure but there are no users treewide. While trying to understand
the motivation and tried to use it, it was found lot of existing custom
attributes can moved to use it instead of device_create_file.

Though most of these never remove/cleanup the custom attribute as they
never call soc_device_unregister, using these custom attribute group
eliminate the need for any cleanup as the driver infrastructure will
take care of that.

Let us remove device_create_file and start using the custom attribute
group in soc_device_attribute.

Link: https://lore.kernel.org/r/20200523170859.50003-7-sudeep.holla@arm.com
Cc: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/soc/ux500/ux500-soc-id.c

@@ -157,6 +157,13 @@ process_show(struct device *dev, struct device_attribute *attr, char *buf)
 
 static DEVICE_ATTR_RO(process);
 
+static struct attribute *ux500_soc_attrs[] = {
+	&dev_attr_process.attr,
+	NULL
+};
+
+ATTRIBUTE_GROUPS(ux500_soc);
+
 static const char *db8500_read_soc_id(struct device_node *backupram)
 {
 	void __iomem *base;
@@ -185,11 +192,11 @@ static void __init soc_info_populate(struct soc_device_attribute *soc_dev_attr,
 	soc_dev_attr->machine  = ux500_get_machine();
 	soc_dev_attr->family   = ux500_get_family();
 	soc_dev_attr->revision = ux500_get_revision();
+	soc_dev_attr->custom_attr_group = ux500_soc_groups[0];
 }
 
 static int __init ux500_soc_device_init(void)
 {
-	struct device *parent;
 	struct soc_device *soc_dev;
 	struct soc_device_attribute *soc_dev_attr;
 	struct device_node *backupram;
@@ -215,9 +222,6 @@ static int __init ux500_soc_device_init(void)
 		return PTR_ERR(soc_dev);
 	}
 
-	parent = soc_device_to_device(soc_dev);
-	device_create_file(parent, &dev_attr_process);
-
 	return 0;
 }
 subsys_initcall(ux500_soc_device_init);