[MIR Serialization] static -> static const in getSerializable*MachineOperandTargetFlags

Make the arrays 'static const' instead of just 'static'. Post-commit review
comment from Roman Divacky on IRC. NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@246376 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed