[AMDGPU] Add two TSFlags: IsAtomicNoRtn and IsAtomicRtn

We are using AtomicNoRet map in multiple places to determine
if an instruction atomic, rtn or nortn atomic. This method
does not work always since we have some instructions which
only has rtn or nortn version.

One such instruction is ds_wrxchg_rtn_b32 which does not have
nortn version. This has caused changes in memory legalizer
tests.

Differential Revision: https://reviews.llvm.org/D96639