Atomic optimizer is turned on by default through D152649. This patch
removes the usage of old command line option amdgpu-atomic-optimizations
and transfer the responsibility to `amdgpu-atomic-optimizer-strategy`.
We can safely remove old option when LLPC remove its all usage.
Reviewed By: foad, arsenm, #amdgpu, cdevadas
Differential Revision: https://reviews.llvm.org/D153007
We have a single noret intrinsic an a lot of special handling
around it. Declare it just as any other but do not define rtn
instructions itself instead.
Differential Revision: https://reviews.llvm.org/D87719
