[CodeGen] Print MI without a newline when skipping debugloc. NFC.

This matches the behavior for skip-operands. While there, document it.
This is a follow-up to r296007.

llvm-svn: 296011
diff --git a/llvm/lib/CodeGen/MachineInstr.cpp b/llvm/lib/CodeGen/MachineInstr.cpp
index acd61dd..f1e1656 100644
--- a/llvm/lib/CodeGen/MachineInstr.cpp
+++ b/llvm/lib/CodeGen/MachineInstr.cpp
@@ -1988,7 +1988,9 @@
     }
     if (isIndirectDebugValue())
       OS << " indirect";
-  } else if (debugLoc && MF && !SkipDebugLoc) {
+  } else if (SkipDebugLoc) {
+    return;
+  } else if (debugLoc && MF) {
     if (!HaveSemi)
       OS << ";";
     OS << " dbg:";