drm/i915/buddy: use kmemleak_update_trace

Since nodes are cached in a free-list, and potentially marked as free
without actually being destroyed, thus allowing them to be
opportunistically re-allocated, we should apply kmemleak_update_trace
every time a node is given a new owner and marked as allocated, to aid
in debugging.

Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190816105357.14340-2-matthew.auld@intel.com