time: delete comments that refer to noexistent symbols

Function do_timer_interrupt_hook() don't take argument regs,
and structure hrtimer_sleeper don't have member cb_pending.
So delete comments refering to these symbols.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Adrian Bunk <bunk@kernel.org>