All of the FF-related resources belong to corresponding FF device, so
they should be freed as a part of hidpp_ff_destroy() to avoid
potential race condidions.

Fixes: ff21a635 ("HID: logitech-hidpp: Force feedback support for the Logitech G920")
Suggested-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc: Henrik Rydberg <rydberg@bitmath.org>
Cc: Pierre-Loup A. Griffais <pgriffais@valvesoftware.com>
Cc: Austin Palmer <austinp@valvesoftware.com>
Cc: linux-input@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org # 5.2+
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>