drm/i915/gt: Fix memory leaks in per-gt sysfs

drm/i915/gt: Fix memory leaks in per-gt sysfs

All kmalloc'd kobjects need a kobject_put() to free memory. For example in
previous code, kobj_gt_release() never gets called. The requirement of
kobject_put() now results in a slightly different code organization.

v2: s/gtn/gt/ (Andi)

Fixes: b770bcfae9ad ("drm/i915/gt: create per-tile sysfs interface")
Signed-off-by: Ashutosh Dixit <[email protected]>
Reviewed-by: Andi Shyti <[email protected]>
Acked-by: Andrzej Hajda <[email protected]>
Signed-off-by: Tvrtko Ursulin <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/a6f6686517c85fba61a0c45097f5bb4fe7e257fb.1653484574.git.ashutosh.dixit@intel.com
(cherry picked from commit 69d6bf5c3754ffc491896632438417d1cedc2c68)
Signed-off-by: Jani Nikula <[email protected]>