Tickless idle is not yet supported. We program the timer period
to the desired system clock tick rate (sys_clock_hw_cycles_per_tick).
This was renamed to the same name used in the Altera Embedded IP
Peripherals Guide; used by other CPUs than Nios II.
Change-Id: Ic4fca8c16b923295b77b63f98f45cd3483c5f560
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>