tests/kernel/timer/timer_api: Correct tick math for odd freq timers
tests/kernel/timer/timer_api: Correct tick math for odd freq timers

This test sets a timer, busy waits for half the duration, and then
checks the remaining time is correct.  And it correctly does all its
math in tick precision and aligns to a timer interrupt to eliminate
aliasing due to the tick stride.

But it's waiting using k_busy_wait(), not a timer: "half the duration"
in MICROSECONDS (for k_busy_wait()) is not necessarily representable
as an integer number of TICKS on all platforms.  Because k_busy_wait()
always rounds up, we need one extra tick of buffer on those platforms.

Signed-off-by: Andy Ross <c70f9a6bf6ee0cd69c8af4ce5e6b131945769315@intel.com>

galak/zephyr,nashif/zephyr,finikorg/zephyr,nashif/zephyr,nashif/zephyr,galak/zephyr,nashif/zephyr,galak/zephyr,finikorg/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,finikorg/zephyr,finikorg/zephyr,Vudentz/zephyr,Vudentz/zephyr