tick/sched: Fix various kernel-doc warnings

tick/sched: Fix various kernel-doc warnings

Fix a slew of kernel-doc warnings in tick-sched.c:

  tick-sched.c:650: warning: Function parameter or struct member 'now' not described in 'tick_nohz_update_jiffies'
  tick-sched.c:741: warning: No description found for return value of 'get_cpu_idle_time_us'
  tick-sched.c:767: warning: No description found for return value of 'get_cpu_iowait_time_us'
  tick-sched.c:1210: warning: No description found for return value of 'tick_nohz_idle_got_tick'
  tick-sched.c:1228: warning: No description found for return value of 'tick_nohz_get_next_hrtimer'
  tick-sched.c:1243: warning: No description found for return value of 'tick_nohz_get_sleep_length'
  tick-sched.c:1282: warning: Function parameter or struct member 'cpu' not described in 'tick_nohz_get_idle_calls_cpu'
  tick-sched.c:1282: warning: No description found for return value of 'tick_nohz_get_idle_calls_cpu'
  tick-sched.c:1294: warning: No description found for return value of 'tick_nohz_get_idle_calls'
  tick-sched.c:1577: warning: Function parameter or struct member 'hrtimer' not described in 'tick_setup_sched_timer'
  tick-sched.c:1577: warning: Excess function parameter 'mode' description in 'tick_setup_sched_timer'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20240331172652.14086-5-rdunlap@infradead.org