[RISCV][NFC] Add CHECK lines for atomic operations on RV64I

As or RV32I, we include these for completeness. Committing now to make it
easier to review the RV64A patch.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@350962 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed