This reverts commit 2bc709d4b9.
Commit 2bc709d4b9 was intended to handle the case where up_timer_gettime may not start from zero case. However, this change has the side-effect of breaking every implementation of tickless mode: After this change the tickless timer structures are used before they are initialized in clock_inittime(). Initialization happens later when up_initialize is called() when arm_timer_initialize().
Since the tickless mode timer is very special, one solution might be to
1. Rename xxx_timer_initialize to up_timer_initialize
2 Move up_timer_initialize to include/nuttx/arch.h
3. Call it from clock subsystem instead up_initialize
Basically, this change make timer initialization almost same as rtc initialization(up_rtc_initialize).
For now, however, we just need to revert the change.