SystemZ: Avoid implicit iterator conversions, NFC

Avoid implicit conversions from MachineInstrBundleIterator to
MachineInstr* in the SystemZ backend, mainly by preferring MachineInstr&
over MachineInstr* and using range-based for loops.

llvm-svn: 275137
diff --git a/llvm/lib/Target/SystemZ/SystemZLDCleanup.cpp b/llvm/lib/Target/SystemZ/SystemZLDCleanup.cpp
index ff81e6b..2cdf2f9 100644
--- a/llvm/lib/Target/SystemZ/SystemZLDCleanup.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZLDCleanup.cpp
@@ -95,9 +95,9 @@
     switch (I->getOpcode()) {
       case SystemZ::TLS_LDCALL:
         if (TLSBaseAddrReg)
-          I = ReplaceTLSCall(I, TLSBaseAddrReg);
+          I = ReplaceTLSCall(&*I, TLSBaseAddrReg);
         else
-          I = SetRegister(I, &TLSBaseAddrReg);
+          I = SetRegister(&*I, &TLSBaseAddrReg);
         Changed = true;
         break;
       default: