[CodeGen] Rename MachineInstrBuilder::addOperand. NFC

Rename from addOperand to just add, to match the other method that has been
added to MachineInstrBuilder for adding more than just 1 operand.

See https://reviews.llvm.org/D28057 for the whole discussion.

Differential Revision: https://reviews.llvm.org/D28556

llvm-svn: 291891
diff --git a/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp b/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
index 0f1b2ed..a0c1a4f 100644
--- a/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
+++ b/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -1785,7 +1785,7 @@
     MachineInstr *CopyMI = BuildMI(*MI.getParent(), MI, MI.getDebugLoc(),
                                    TII->get(TargetOpcode::COPY))
                                .addReg(DstReg, RegState::Define, SubIdx)
-                               .addOperand(UseMO);
+                               .add(UseMO);
 
     // The first def needs an <undef> flag because there is no live register
     // before it.