[M68KNOMMU]: cleanup m68knommu timer code

Reduce the function pointer mess of the m68knommu timer code. Call direct to the local hardware's timer setup, and expose the local common timer interrupt handler to the lower level hardware timer. Ultimately this will save definitions of all these functions across all the platform code to setup th

[M68KNOMMU]: cleanup m68knommu timer code

Reduce the function pointer mess of the m68knommu timer code. Call direct to the local hardware's timer setup, and expose the local common timer interrupt handler to the lower level hardware timer. Ultimately this will save definitions of all these functions across all the platform code to setup th