clocksource/drivers/cadence-ttc: Fix some kernel-doc warnings

Fix some function kernel-doc warnings to placate scripts/kernel-doc.

timer-cadence-ttc.c:79: warning: Function parameter or member 'clk_rate_change_nb' not described in 'ttc_timer'
timer-cadence-ttc.c:158: warning: Function parameter or member 'cs' not described in '__ttc_clocksource_read'
timer-cadence-ttc.c:194: warning: expecting prototype for ttc_set_{shutdown|oneshot|periodic}(). Prototype was for ttc_shutdown() instead
timer-cadence-ttc.c:196: warning: No description found for return value of 'ttc_shutdown'
timer-cadence-ttc.c:212: warning: No description found for return value of 'ttc_set_periodic'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Michal Simek <michal.simek@amd.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arm-kernel@lists.infradead.org
Acked-by: Michal Simek <michal.simek@amd.com>
Tested-by: Michal Simek <michal.simek@amd.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20231205230448.772-1-rdunlap@infradead.org