timers: Update schedule_[hr]timeout*() related function descriptions

schedule_timeout*() functions do not have proper kernel-doc formatted
function descriptions. schedule_hrtimeout() and schedule_hrtimeout_range()
have a almost identical description.

Add missing function descriptions. Remove copy of function description and
add a pointer to the existing description instead.

Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20241014-devel-anna-maria-b4-timers-flseep-v3-3-dc8b907cb62f@linutronix.de