hwmon: (gsc-hwmon) Switch to flexible array to simplify code

Using flexible array is more straight forward. It
  - saves 1 pointer in the 'gsc_hwmon_platform_data' structure
  - saves an indirection when using this array
  - saves some LoC and avoids some always spurious pointer arithmetic
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/61a23e1d642397cfcecc4ac3bb0ab485d257987d.1668936855.git.christophe.jaillet@wanadoo.frSigned-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/gsc-hwmon.c

@@ -257,13 +257,10 @@ gsc_hwmon_get_devtree_pdata(struct device *dev)
 	if (nchannels == 0)
 		return ERR_PTR(-ENODEV);
 
-	pdata = devm_kzalloc(dev,
-			     sizeof(*pdata) + nchannels * sizeof(*ch),
+	pdata = devm_kzalloc(dev, struct_size(pdata, channels, nchannels),
 			     GFP_KERNEL);
 	if (!pdata)
 		return ERR_PTR(-ENOMEM);
-	ch = (struct gsc_hwmon_channel *)(pdata + 1);
-	pdata->channels = ch;
 	pdata->nchannels = nchannels;
 
 	/* fan controller base address */
@@ -277,6 +274,7 @@ gsc_hwmon_get_devtree_pdata(struct device *dev)
 
 	of_node_put(fan);
 
+	ch = pdata->channels;
 	/* allocate structures for channels and count instances of each type */
 	device_for_each_child_node(dev, child) {
 		if (fwnode_property_read_string(child, "label", &ch->name)) {

include/linux/platform_data/gsc_hwmon.h

@@ -29,18 +29,17 @@ struct gsc_hwmon_channel {
 
 /**
  * struct gsc_hwmon_platform_data - platform data for gsc_hwmon driver
- * @channels:	pointer to array of gsc_hwmon_channel structures
- *		describing channels
  * @nchannels:	number of elements in @channels array
  * @vreference: voltage reference (mV)
  * @resolution: ADC bit resolution
  * @fan_base: register base for FAN controller
+ * @channels:	array of gsc_hwmon_channel structures describing channels
  */
 struct gsc_hwmon_platform_data {
-	const struct gsc_hwmon_channel *channels;
 	int nchannels;
 	unsigned int resolution;
 	unsigned int vreference;
 	unsigned int fan_base;
+	struct gsc_hwmon_channel channels[];
 };
 #endif