clocksource/drivers/timer-rtl-otto: Drop set_counter function

The current counter value is a read only register. It will be
reset when writing a new target timer value with rttm_set_period().
rttm_set_counter() is essentially a noop. Drop it.

While this makes rttm_start_timer() and rttm_enable_timer() the
same functions keep both to make the established abstraction layers
for register and control functions active.

Downstream has already tested and confirmed a patch. See
openwrt/openwrt#19468
https://forum.openwrt.org/t/support-for-rtl838x-based-managed-switches/57875/3788

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Tested-by: Stephen Howell <howels@allthatwemight.be>
Tested-by: Bjørn Mork <bjorn@mork.no>
Link: https://lore.kernel.org/r/20250804080328.2609287-3-markus.stockhausen@gmx.de

Author: plappermaul

drivers/clocksource/timer-rtl-otto.c

@@ -56,11 +56,6 @@ struct rttm_cs {
 };
 
 /* Simple internal register functions */
-static inline void rttm_set_counter(void __iomem *base, unsigned int counter)
-{
-	iowrite32(counter, base + RTTM_CNT);
-}
-
 static inline unsigned int rttm_get_counter(void __iomem *base)
 {
 	return ioread32(base + RTTM_CNT);
@@ -137,7 +132,6 @@ static void rttm_stop_timer(void __iomem *base)
 
 static void rttm_start_timer(struct timer_of *to, u32 mode)
 {
-	rttm_set_counter(to->of_base.base, 0);
 	rttm_enable_timer(to->of_base.base, mode, to->of_clk.rate / RTTM_TICKS_PER_SEC);
 }