CVE-2026-99210: accel/rocket: clear rdev on device init failure

In the Linux kernel, the following vulnerability has been resolved:

accel/rocket: clear rdev on device init failure

rocketprobe() stores the return value from rocketdeviceinit() in the file-scoped rdev pointer before checking whether it is an error pointer. If rocketdeviceinit() fails, rdev is left as an ERRPTR.

The rdev pointer is also used as the marker for whether the shared rocket device has already been initialized. A later core probe can therefore see a non-NULL rdev, skip rocketdeviceinit(), and dereference the error pointer when reading rdev->numcores.

Save the error code and clear rdev before returning from the rocketdeviceinit() failure path.