CellSPU:

- First patch from Nehal Desai, a new contributor at Aerospace. Nehal's patch
  fixes sign/zero/any-extending loads for integers and floating point. Example
  code, compiled w/o debugging or optimization where he first noticed the bug:

  int main(void) {
    float a = 99.0;
    printf("%d\n", a);
    return 0;
  }

  Verified that this code actually works on a Cell SPU.

Changes by Scott Michel:
- Fix bug in the value type list constructed by SPUISD::LDRESULT to include
  both the load result's result and chain, not just the chain alone.
- Simplify LowerLOAD and remove extraneous and unnecessary chains.
- Remove unused SPUISD pseudo instructions.

llvm-svn: 60526