Micro-optimize spitfire_block_{copy,zero}(): - Predict the loop as taken as it's more likely that there's still   data to copy and memory to zero respectively. - Don't waste the delay slot.
Micro-optimize spitfire_block_{copy,zero}():
- Predict the loop as taken as it's more likely that there's still
  data to copy and memory to zero respectively.
- Don't waste the delay slot.

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