drivers: timer: smartbond: Fix timer2 timeout set

When function sys_clock_set_timout() is called with small value
(i.e. 1) calculated time to be programmed to TIMER2 reload
register may be such that is expires before code set's it
up. In that case timer interrupt will be scheduled in far
future.

With this change, code checks after it sets reload value if
requested time already passed and if so TIMER2 interrupt
is marked as pending to avoid races.

Signed-off-by: Jerzy Kasenberg <jerzy.kasenberg@codecoup.pl>