usb: gadget: f_fs: remove redundant ffs_data_get()

commit a3058a5d upstream.

During FunctionFS bind, ffs_data_get() function was called twice
(in functionfs_bind() and in ffs_do_functionfs_bind()), while on unbind
ffs_data_put() was called once (in functionfs_unbind() function).
In result refcount never reached value 0, and ffs memory resources has
been never released.

Since ffs_data_get() call in ffs_do_functionfs_bind() is redundant
and not neccessary, we remove it to have equal number of gets ans puts,
and free allocated memory after refcount reach 0.

Fixes: 5920cda6 (usb: gadget: FunctionFS: convert to new function
	interface with backward compatibility)
Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
[ luis: backported to 3.16: file rename:
  drivers/usb/gadget/function/f_fs.c -> drivers/usb/gadget/f_fs.c ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/usb/gadget/f_fs.c

@@ -2297,8 +2297,6 @@ static inline struct f_fs_opts *ffs_do_functionfs_bind(struct usb_function *f,
 	func->conf = c;
 	func->gadget = c->cdev->gadget;
 
-	ffs_data_get(func->ffs);
-
 	/*
 	 * in drivers/usb/gadget/configfs.c:configfs_composite_bind()
 	 * configurations are bound in sequence with list_for_each_entry,