sched/core: Optimize core cookie matching check

sched/core: Optimize core cookie matching check

Early return true if the core cookie matches. This avoids the SMT mask
loop to check for an idle core, which might be more expensive on wide
platforms.

Signed-off-by: Fernand Sieber <sieberf@amazon.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Reviewed-by: Madadi Vineeth Reddy <vineethr@linux.ibm.com>
Link: https://patch.msgid.link/20251105152538.470586-1-sieberf@amazon.com