ac/nir: fix intrinsic names for atomic operations with LLVM 9+

ac/nir: fix intrinsic names for atomic operations with LLVM 9+

This fixes the following LLVM error when using RADV_DEBUG=checkir:
Intrinsic name not mangled correctly for type arguments! Should be: llvm.amdgcn.buffer.atomic.add.i32
i32 (i32, <4 x i32>, i32, i32, i1)* @llvm.amdgcn.buffer.atomic.add

The cmpswap operation still uses the old intrinsic.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>