[CodeGen][NFC] Refactor MachineInstr::print

* Handle more cases where the MI is not attached yet
* Add similar asserts like in MIRPrinter::print

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@322848 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed