USB: gadget: f_fs: functionfs_add() renamed to functionfs_bind_config()

FunctionFS had a bit unique name for function used to add it
to USB configuration.  Renamed as to match naming convention
of other functions.

Signed-off-by: Michal Nazarewicz <m.nazarewicz@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/include/linux/usb/functionfs.h b/include/linux/usb/functionfs.h
index a34a2a0..6f649c1 100644
--- a/include/linux/usb/functionfs.h
+++ b/include/linux/usb/functionfs.h
@@ -180,9 +180,9 @@
 static void functionfs_unbind(struct ffs_data *ffs)
 	__attribute__((nonnull));
 
-static int functionfs_add(struct usb_composite_dev *cdev,
-			  struct usb_configuration *c,
-			  struct ffs_data *ffs)
+static int functionfs_bind_config(struct usb_composite_dev *cdev,
+				  struct usb_configuration *c,
+				  struct ffs_data *ffs)
 	__attribute__((warn_unused_result, nonnull));