Revert "[AArch64][GlobalISel] Legalize ctpop s128"

This reverts commit 97e95fea53fc403c2a12e356dc835fc922123575.

It broke test/CodeGen/Mips/GlobalISel/llvm-ir/ctpop.ll. Not sure why I didn't see that.
diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 8286f4f..38b2b23 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -5656,15 +5656,7 @@
 
     auto LoCTPOP = MIRBuilder.buildCTPOP(DstTy, UnmergeSrc.getReg(0));
     auto HiCTPOP = MIRBuilder.buildCTPOP(DstTy, UnmergeSrc.getReg(1));
-
-    LLT CountTy = LLT::scalar(Log2_64_Ceil(SrcTy.getSizeInBits()));
-    if (CountTy.getSizeInBits() < DstTy.getSizeInBits()) {
-      LoCTPOP = MIRBuilder.buildTrunc(CountTy, LoCTPOP);
-      HiCTPOP = MIRBuilder.buildTrunc(CountTy, HiCTPOP);
-      auto Add = MIRBuilder.buildAdd(CountTy, HiCTPOP, LoCTPOP);
-      MIRBuilder.buildZExt(DstReg, Add);
-    } else
-      MIRBuilder.buildAdd(DstReg, HiCTPOP, LoCTPOP);
+    MIRBuilder.buildAdd(DstReg, HiCTPOP, LoCTPOP);
 
     MI.eraseFromParent();
     return Legalized;