[AMDGPU] Tweak VOP3_INTERP16 profile

[foad]

Summary

Set the output register class based on the output type, instead of
hard-coding VGPR_32. I think this is more correct. It doesn't make any
difference at the moment because we use the same class for 16- and
32-bit results, but it might in future if we make more use of true
16-bit register classes.

llvm/lib/Target/AMDGPU/VOP3Instructions.td

dag ret = !if(HasSrc2,
             );
 }
 
 class VOP3_INTERP16 <list<ValueType> ArgVT> : VOPProfile<ArgVT> {
 
   let HasOMod = !ne(DstVT.Value, f16.Value);
   let HasHigh = 1;
 
-  let Outs64 = (outs VGPR_32:$vdst);
+  let Outs64 = (outs DstRC.RegClass:$vdst);
   let Ins64 = getInterp16Ins<HasSrc2, HasOMod, Src0Mod, Src2Mod>.ret;
   let Asm64 = getInterp16Asm<HasSrc2, HasOMod>.ret;
 }
 
 //===----------------------------------------------------------------------===//
 // VOP3 Instructions
 //===----------------------------------------------------------------------===//