[PlaceSafepoints] Cleanup InsertSafepointPoll function

While working on another change, I noticed that the naming in this function was mildly deceptive.  While fixing that, I took the oppurtunity to modernize some of the code.  NFC intended.

llvm-svn: 238252
diff --git a/llvm/lib/IR/Instruction.cpp b/llvm/lib/IR/Instruction.cpp
index 57c143c..45bb296 100644
--- a/llvm/lib/IR/Instruction.cpp
+++ b/llvm/lib/IR/Instruction.cpp
@@ -58,6 +58,11 @@
   return getParent()->getModule();
 }
 
+Module *Instruction::getModule() {
+  return getParent()->getModule();
+}
+
+
 void Instruction::removeFromParent() {
   getParent()->getInstList().remove(this);
 }