hrtimer: Use hrtimer_cb_get_time() helper

Various other helpers contain open-coded implementations of
hrtimer_cb_get_time(). This prevents refactoring the implementation.

Reuse the existing helper.

For this to work, move hrtimer_cb_get_time() a bit up in the file and also
make its argument 'const'.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20250821-hrtimer-cleanup-get_time-v2-7-3ae822e5bfbd@linutronix.de

Author: t-8ch

include/linux/hrtimer.h

@@ -154,14 +154,14 @@ static inline s64 hrtimer_get_expires_ns(const struct hrtimer *timer)
 	return ktime_to_ns(timer->node.expires);
 }
 
-static inline ktime_t hrtimer_expires_remaining(const struct hrtimer *timer)
+static inline ktime_t hrtimer_cb_get_time(const struct hrtimer *timer)
 {
-	return ktime_sub(timer->node.expires, timer->base->get_time());
+	return timer->base->get_time();
 }
 
-static inline ktime_t hrtimer_cb_get_time(struct hrtimer *timer)
+static inline ktime_t hrtimer_expires_remaining(const struct hrtimer *timer)
 {
-	return timer->base->get_time();
+	return ktime_sub(timer->node.expires, hrtimer_cb_get_time(timer));
 }
 
 static inline int hrtimer_is_hres_active(struct hrtimer *timer)
@@ -200,8 +200,7 @@ __hrtimer_expires_remaining_adjusted(const struct hrtimer *timer, ktime_t now)
 static inline ktime_t
 hrtimer_expires_remaining_adjusted(const struct hrtimer *timer)
 {
-	return __hrtimer_expires_remaining_adjusted(timer,
-						    timer->base->get_time());
+	return __hrtimer_expires_remaining_adjusted(timer, hrtimer_cb_get_time(timer));
 }
 
 #ifdef CONFIG_TIMERFD
@@ -363,7 +362,7 @@ hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval);
 static inline u64 hrtimer_forward_now(struct hrtimer *timer,
 				      ktime_t interval)
 {
-	return hrtimer_forward(timer, timer->base->get_time(), interval);
+	return hrtimer_forward(timer, hrtimer_cb_get_time(timer), interval);
 }
 
 /* Precise sleep: */