sched_ext: Relocate scx_bpf_task_cgroup() and its BTF_ID to the end of kfunc section

sched_ext: Relocate scx_bpf_task_cgroup() and its BTF_ID to the end of kfunc section

Move scx_bpf_task_cgroup() kfunc definition and its BTF_ID entry to the end
of the kfunc section before __bpf_kfunc_end_defs() for cleaner code
organization.

No functional changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Reviewed-by: Andrea Righi <arighi@nvidia.com>