sched/core: Use do-while instead of for loop in set_nr_if_polling()

Use equivalent do-while loop instead of infinite for loop.

There are no asm code changes.

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230228161426.4508-1-ubizjak@gmail.com