[IR] Optimize no-op removal from AttributeSet (NFC)

When removing an AttrBuilder from an AttributeSet, first check
whether there is any overlap. If nothing is being removed, we can
directly return the original set.

llvm/lib/IR/Attributes.cpp

@@ -781,8 +781,12 @@ AttributeSet AttributeSet::removeAttribute(LLVMContext &C,
 }
 
 AttributeSet AttributeSet::removeAttributes(LLVMContext &C,
-                                              const AttrBuilder &Attrs) const {
+                                            const AttrBuilder &Attrs) const {
   AttrBuilder B(*this);
+  // If there is nothing to remove, directly return the original set.
+  if (!B.overlaps(Attrs))
+    return *this;
+
   B.remove(Attrs);
   return get(C, B);
 }