sched_ext: Change find_global_dsq() to take CPU number instead of task

sched_ext: Change find_global_dsq() to take CPU number instead of task

Change find_global_dsq() to take a CPU number directly instead of a task
pointer. This prepares for callers where the CPU is available but the task is
not.

No functional changes.

v2: Rename tcpu to cpu in find_global_dsq() (Emil Tsalapatis).

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>