[MLIR][NVVM] Add nvvm.addf and nvvm.subf Ops (#179162)
Adds `nvvm.addf` and `nvvm.subf` Ops to the NVVM dialect. `nvvm.addf`
performs a floating-point addition between two operands. `nvvm.subf`
performs a floating-point subtraction between two operands and is
equivalent to an `llvm.fneg` followed by an `nvvm.addf` operation.
PTX ISA Reference:
1.
https://docs.nvidia.com/cuda/parallel-thread-execution/#floating-point-instructions-add
2.
https://docs.nvidia.com/cuda/parallel-thread-execution/#half-precision-floating-point-instructions-add
