sched/fair: Get this cpu once in find_new_ilb()

sched/fair: Get this cpu once in find_new_ilb()

Calling smp_processor_id() on:
 - In CONFIG_DEBUG_PREEMPT=y, if preemption/irq is disabled, then it does
   not print any warning.
 - In CONFIG_DEBUG_PREEMPT=n, it doesn't do anything apart from getting
   __smp_processor_id

So with both CONFIG_DEBUG_PREEMPT=y/n, in preemption disabled section
it is better to cache the value. It could save a few cycles. Though
tiny, repeated in loop could add up to a small value.

find_new_ilb is called in interrupt context. So preemption is disabled.
So Hoist the this_cpu out of loop

Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Mukesh Kumar Chaurasiya (IBM) <mkchauras@gmail.com>
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Link: https://patch.msgid.link/20260323193630.640311-2-sshegde@linux.ibm.com