This is subsequent patch of D72755.
module-target-abi2.ll testcase want to address a problem about TargetABI info in RISCVAsmBackend will not update after getSubtargetImpl create a new subtarget.
so RISCVELFStreamer will get the older TargetABI value from RISCVAsmBackend.
module-target-abi.ll doesn't have this problem because the default TargetABI value is equal to target-abi module flag.