Originally FFS_FL_CALL_CLOSED_CALLBACK flag has been used to
indicate if we should call ffs_closed_callback().

Commit 4b187fce ("usb: gadget: FunctionFS: add devices
management code") changed its semantic to indicate if we should
call ffs_closed() function which does a little bit more.

This situation leads to:

[  122.362269] ------------[ cut here ]------------
[  122.362287] WARNING: CPU: 2 PID: 2384 at drivers/usb/gadget/function/f_fs.c:3417 ffs_ep0_write+0x730/0x810 [usb_f_fs]()
[  122.362292] Modules linked in:
[  122.362555] CPU: 2 PID: 2384 Comm: adbd Tainted: G        W       4.1.0-0.rc4.git0.1.1.fc22.i686 #1
[  122.362561] Hardware name: To be filled by O.E.M. To be filled by O.E.M./Aptio CRB, BIOS 5.6.5 07/25/2014
[  122.362567]  c0d1f947 415badfa 00000000 d1029e64 c0a86e54 00000000 d1029e94 c045b937
[  122.362584]  c0c37f94 00000002 00000950 f9b313d4 00000d59 f9b2ebf0 f9b2ebf0 fffffff0
[  122.362600]  00000003 deb53d00 d1029ea4 c045ba42 00000009 00000000 d1029f08 f9b2ebf0
[  122.362617] Call Trace:
[  122.362633]  [<c0a86e54>] dump_stack+0x41/0x52
[  122.362645]  [<c045b937>] warn_slowpath_common+0x87/0xc0
[  122.362658]  [<f9b2ebf0>] ? ffs_ep0_write+0x730/0x810 [usb_f_fs]
[  122.362668]  [<f9b2ebf0>] ? ffs_ep0_write+0x730/0x810 [usb_f_fs]
[  122.362678]  [<c045ba42>] warn_slowpath_null+0x22/0x30
[  122.362689]  [<f9b2ebf0>] ffs_ep0_write+0x730/0x810 [usb_f_fs]
[  122.362702]  [<f9b2e4c0>] ? ffs_ep0_read+0x380/0x380 [usb_f_fs]
[  122.362712]  [<c05a1c1f>] __vfs_write+0x2f/0x100
[  122.362722]  [<c05a42f2>] ? __sb_start_write+0x52/0x110
[  122.362731]  [<c05a2534>] vfs_write+0x94/0x1b0
[  122.362740]  [<c0a8a1c0>] ? mutex_lock+0x10/0x30
[  122.362749]  [<c05a2f41>] SyS_write+0x51/0xb0
[  122.362759]  [<c0a8c71f>] sysenter_do_call+0x12/0x12
[  122.362766] ---[ end trace 0673d3467cecf8db ]---

in some cases (reproduction path below). This commit get back
semantic of that flag and ensures that ffs_closed() is called
always when needed but ffs_closed_callback() is called only
if this flag is set.

Reproduction path:
Compile kernel without any UDC driver or bound some gadget
to existing one and then:

$ modprobe g_ffs
$ mount none -t functionfs mount_point
$ ffs-example mount_point

This will fail with -ENODEV as there is no udc.

$ ffs-example mount_point

This will fail with -EBUSY because ffs_data has not been
properly cleaned up.
Signed-off-by: Krzysztof Opasiak <k.opasiak@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>