[MachineInstrBundle] Actually set the PartialDeadDef flag only when the register
is defined!

The users were checking the proper thing (Defined + PartialDeadDef), but the
information may have been wrong for other use cases, so fix that.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267641 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed