drm/syncobj: Fix memory leak in drm_syncobj_find_fence()

drm/syncobj: Fix memory leak in drm_syncobj_find_fence()

Commit 18226ba52159 ("drm/syncobj: reject invalid flags in
drm_syncobj_find_fence") forgot to take into account the fact that
drm_syncobj_find() takes a reference to syncobj and returns early
without dropping the reference, leading to memory leaks.

Fixes: 18226ba52159 ("drm/syncobj: reject invalid flags in drm_syncobj_find_fence")
Reported by: Sam Spencer <sam.spencer@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>
Acked-by: Erik Kurzinger <ekurzinger@gmail.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://lore.kernel.org/all/20260507144425.2488057-1-liviu.dudau@arm.com