Revert "Revert "Set FP RoundToZero for interp f16 instructions""
Revert "Revert "Set FP RoundToZero for interp f16 instructions""

The theory is that this was causing fp16 interpolation failures in
testing.

This reverts commit 452fa2c445e449df9633abdb28dac61982ed71a2.

Change-Id: Iacf462bf6ba37a26d01bacce3d93cf16832ef40a

GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm