timekeeping: Add missing kernel-doc function comments

Fixup the incomplete kernel-doc style comments for do_adjtimex() and
hardpps() by documenting the function parameters.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240607090656.104883-1-yang.lee@linux.alibaba.com
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=9301