Revert "IR: add optional type to 'byval' function parameters"

The IRLinker doesn't delve into the new byval attribute when mapping types, and
this breaks LTO.

llvm-svn: 362029
diff --git a/llvm/lib/CodeGen/GlobalISel/CallLowering.cpp b/llvm/lib/CodeGen/GlobalISel/CallLowering.cpp
index 9372740..f144b18 100644
--- a/llvm/lib/CodeGen/GlobalISel/CallLowering.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/CallLowering.cpp
@@ -87,10 +87,7 @@
 
   if (Arg.Flags.isByVal() || Arg.Flags.isInAlloca()) {
     Type *ElementTy = cast<PointerType>(Arg.Ty)->getElementType();
-
-    auto Ty = Attrs.getAttribute(OpIdx, Attribute::ByVal).getValueAsType();
-    Arg.Flags.setByValSize(DL.getTypeAllocSize(Ty ? Ty : ElementTy));
-
+    Arg.Flags.setByValSize(DL.getTypeAllocSize(ElementTy));
     // For ByVal, alignment should be passed from FE.  BE will guess if
     // this info is not there but there are cases it cannot get right.
     unsigned FrameAlign;