CRIS v32: Update and simplify kernel/irq.c.

- First timer register has changed name to timer0.
- Build IRQs with only IRQ number, mask bit will be calculated instead.
- Add more IRQs, up to 64 supported.
- Use arrays to hold which IRQs triggered instead of trying to do magic
  with two 32 bit values now that more than 32 IRQs are supported.