sched/nohz: Use consistent variable names in find_new_ilb() and kick_ilb()

Use 'ilb_cpu' consistently in both functions.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Link: https://lore.kernel.org/r/20231006102518.2452758-3-mingo@kernel.org