Input: ims-pcu - fix use-after-free and double-free in disconnect

ims_pcu_disconnect() only intended to perform cleanup when the primary
(control) interface is unbound. However, it currently relies on the
interface class to distinguish between control and data interfaces.
A malicious device could present a data interface with the same class
as the control interface, leading to premature cleanup and potential
use-after-free or double-free.

Switch to verifying that the interface being disconnected is indeed
the control interface.

Fixes: 628329d52474 ("Input: add IMS Passenger Control Unit driver")
Cc: stable@vger.kernel.org
Reported-by: Sashiko bot <sashiko-bot@kernel.org>
Assisted-by: Gemini:gemini-3.1-pro
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>