Input: ims-pcu - add response length checks

The driver processes response data from device buffers without verifying
that the device actually sent enough data. This can lead to
out-of-bounds reads or processing stale data.

Add checks for the expected response length before accessing the
buffers.

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>