CVE-2026-72361: drm/xe/hw_engine: Fix double-free of managed BO in error path

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

drm/xe/hwengine: Fix double-free of managed BO in error path

The error path in hwengineinit() explicitly frees a BO allocated with xemanagedbocreatepinmap() via xebounpinmapnovm(). Since the managed BO already has a devm cleanup action registered, this causes a double-free when devm unwinds during probe failure.

Remove the explicit free and let devm handle it, consistent with all other xemanagedbocreatepinmap() callers.

(cherry picked from commit e459a3bdeb117be496d7f229e2ea1f6c9fe4080b)