drm/malidp: convert platform driver to use dev_groups

Platform drivers now have the option to have the platform core create
and remove any needed sysfs attribute files.  So take advantage of that
and do not register "by hand" a sysfs file.

Cc: Liviu Dudau <liviu.dudau@arm.com>
Cc: Brian Starkey <brian.starkey@arm.com>
Cc: Mali DP Maintainers <malidp@foss.arm.com>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Tested-by: Liviu Dudau <liviu.dudau@arm.com>
Acked-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200517193655.3895087-2-emil.l.velikov@gmail.com

drivers/gpu/drm/arm/malidp_drv.c

@@ -657,20 +657,11 @@ static ssize_t core_id_show(struct device *dev, struct device_attribute *attr,
 
 static DEVICE_ATTR_RO(core_id);
 
-static int malidp_init_sysfs(struct device *dev)
-{
-	int ret = device_create_file(dev, &dev_attr_core_id);
-
-	if (ret)
-		DRM_ERROR("failed to create device file for core_id\n");
-
-	return ret;
-}
-
-static void malidp_fini_sysfs(struct device *dev)
-{
-	device_remove_file(dev, &dev_attr_core_id);
-}
+static struct attribute *mali_dp_attrs[] = {
+	&dev_attr_core_id.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(mali_dp);
 
 #define MAX_OUTPUT_CHANNELS	3
 
@@ -832,10 +823,6 @@ static int malidp_bind(struct device *dev)
 	if (ret < 0)
 		goto query_hw_fail;
 
-	ret = malidp_init_sysfs(dev);
-	if (ret)
-		goto init_fail;
-
 	/* Set the CRTC's port so that the encoder component can find it */
 	malidp->crtc.port = of_graph_get_port_by_id(dev->of_node, 0);
 
@@ -893,8 +880,6 @@ static int malidp_bind(struct device *dev)
 bind_fail:
 	of_node_put(malidp->crtc.port);
 	malidp->crtc.port = NULL;
-init_fail:
-	malidp_fini_sysfs(dev);
 	malidp_fini(drm);
 query_hw_fail:
 	pm_runtime_put(dev);
@@ -927,7 +912,6 @@ static void malidp_unbind(struct device *dev)
 	component_unbind_all(dev, drm);
 	of_node_put(malidp->crtc.port);
 	malidp->crtc.port = NULL;
-	malidp_fini_sysfs(dev);
 	malidp_fini(drm);
 	pm_runtime_put(dev);
 	if (pm_runtime_enabled(dev))
@@ -1023,6 +1007,7 @@ static struct platform_driver malidp_platform_driver = {
 		.name = "mali-dp",
 		.pm = &malidp_pm_ops,
 		.of_match_table	= malidp_drm_of_match,
+		.dev_groups = mali_dp_groups,
 	},
 };