MIR Serialization: Serialize the operand's bit mask target flags.

MIR Serialization: Serialize the operand's bit mask target flags.

This commit adds support for bit mask target flag serialization to the MIR
printer and the MIR parser. It also adds support for the machine operand's
target flag serialization to the AArch64 target.

Reviewers: Duncan P. N. Exon Smith

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@245383 91177308-0d34-0410-b5e6-96231b3b80d8