[MSP430] Align functions on 2-byte boundary instead of 4.

[pftbest]

Summary

There is no benefit in having the 4-byte alignment, and removing this
restriction can save a lot of space for some applications.

[pftbest]

ping

Should I add the tests for this change?

[awygle]

Looks good to me!

lib/Target/MSP430/MSP430ISelLowering.cpp

MSP430TargetLowering::MSP430TargetLowering(const TargetMachine &TM,
   setLibcallCallingConv(RTLIB::UNE_F64, CallingConv::MSP430_BUILTIN);
   setLibcallCallingConv(RTLIB::OGE_F64, CallingConv::MSP430_BUILTIN);
   setLibcallCallingConv(RTLIB::OLT_F64, CallingConv::MSP430_BUILTIN);
   setLibcallCallingConv(RTLIB::OLE_F64, CallingConv::MSP430_BUILTIN);
   setLibcallCallingConv(RTLIB::OGT_F64, CallingConv::MSP430_BUILTIN);
   // TODO: __mspabi_srall, __mspabi_srlll, __mspabi_sllll
 
   setMinFunctionAlignment(1);
-  setPrefFunctionAlignment(2);
+  setPrefFunctionAlignment(1);
 }
 
 SDValue MSP430TargetLowering::LowerOperation(SDValue Op,
                                              SelectionDAG &DAG) const {
   switch (Op.getOpcode()) {
   case ISD::SHL: // FALLTHROUGH
   case ISD::SRL:
   case ISD::SRA:              return LowerShifts(Op, DAG);