nr_timer: consistently pass by ref, rename to nr_timer_is_active()

Pass consistently the NR_timer_t object through a pointer. Since we have
to modify all occurrences of is_nr_timer_active(), we use that occasion
and rename that function to nr_timer_is_active() to make it consistent
with all other functions, starting with nr_timer.

common/utils/nr/nr_common.h

@@ -163,19 +163,19 @@ void nr_timer_setup(NR_timer_t *timer, const uint32_t target, const uint32_t ste
  * @param timer Timer to be checked
  * @return Indication if the timer is expired or not
  */
-bool nr_timer_expired(NR_timer_t timer);
+bool nr_timer_expired(const NR_timer_t *timer);
 /**
  * @brief To check if a timer is active
  * @param timer Timer to be checked
  * @return Indication if the timer is active or not
  */
-bool is_nr_timer_active(NR_timer_t timer);
+bool nr_timer_is_active(const NR_timer_t *timer);
 /**
  * @brief To return how much time has passed since start of timer
  * @param timer Timer to be checked
  * @return Time passed since start of timer
  */
-uint32_t nr_timer_elapsed_time(NR_timer_t timer);
+uint32_t nr_timer_elapsed_time(const NR_timer_t *timer);
 
 
 extern const nr_bandentry_t nr_bandtable[];