[SystemZ] Fix build break from r265689

Fix build error seen on some build bots due to:
error: default label in switch which covers all enumeration values

llvm-svn: 265693
diff --git a/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp b/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
index 0dc32b5..80393a6 100644
--- a/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
@@ -1334,9 +1334,8 @@
     default:
       return 0;
     }
-  default:
-    return 0;
   }
+  return 0;
 }
 
 void SystemZInstrInfo::loadImmediate(MachineBasicBlock &MBB,