MSP430: Avoid implicit iterator conversions, NFC

Avoid implicit conversions from MachineInstrBundleIIterator to
MachineInstr* in the MSP430 backend by preferring MachineInstr& over
MachineInstr* when a pointer isn't nullable.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@274933 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed