usb: gadget: configfs: add cfg_to_gadget_info() helper

add this helper function can simplify code of
config_usb_cfg_link() and config_usb_cfg_unlink().
Signed-off-by: Linyu Yuan <quic_linyyuan@quicinc.com>
Link: https://lore.kernel.org/r/1634649997-28745-2-git-send-email-quic_linyyuan@quicinc.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/configfs.c

@@ -73,6 +73,11 @@ static inline struct config_usb_cfg *to_config_usb_cfg(struct config_item *item)
 			group);
 }
 
+static inline struct gadget_info *cfg_to_gadget_info(struct config_usb_cfg *cfg)
+{
+	return container_of(cfg->c.cdev, struct gadget_info, cdev);
+}
+
 struct gadget_strings {
 	struct usb_gadget_strings stringtab_dev;
 	struct usb_string strings[USB_GADGET_FIRST_AVAIL_IDX];
@@ -413,8 +418,7 @@ static int config_usb_cfg_link(
 	struct config_item *usb_func_ci)
 {
 	struct config_usb_cfg *cfg = to_config_usb_cfg(usb_cfg_ci);
-	struct usb_composite_dev *cdev = cfg->c.cdev;
-	struct gadget_info *gi = container_of(cdev, struct gadget_info, cdev);
+	struct gadget_info *gi = cfg_to_gadget_info(cfg);
 
 	struct config_group *group = to_config_group(usb_func_ci);
 	struct usb_function_instance *fi = container_of(group,
@@ -464,8 +468,7 @@ static void config_usb_cfg_unlink(
 	struct config_item *usb_func_ci)
 {
 	struct config_usb_cfg *cfg = to_config_usb_cfg(usb_cfg_ci);
-	struct usb_composite_dev *cdev = cfg->c.cdev;
-	struct gadget_info *gi = container_of(cdev, struct gadget_info, cdev);
+	struct gadget_info *gi = cfg_to_gadget_info(cfg);
 
 	struct config_group *group = to_config_group(usb_func_ci);
 	struct usb_function_instance *fi = container_of(group,