Input: ims-pcu - fix type confusion in CDC union descriptor parsing

The driver currently trusts the bMasterInterface0 from the CDC union
descriptor without verifying that it matches the interface being
probed. This could lead to the driver overwriting the private data of
another interface.

Validate that the control interface found in the descriptor is indeed
the one we are probing.

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>