Revert "[DAG] SimplifyDemandedBits - simplify rotl/rotr to shl/srl"

This reverts commit 3cf4a2c6.

It makes llc hang on the following test case.
```
target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
target triple = "aarch64-unknown-linux-gnu"

define dso_local void @_PyUnicode_EncodeUTF16() local_unnamed_addr #0 {
entry:
  br label %while.body117.i

while.body117.i:                                  ; preds = %cleanup149.i, %entry
  %out.6269.i = phi i16* [ undef, %cleanup149.i ], [ undef, %entry ]
  %0 = load i16, i16* undef, align 2
  %1 = icmp eq i16 undef, -10240
  br i1 %1, label %fail.i, label %cleanup149.i

cleanup149.i:                                     ; preds = %while.body117.i
  %or130.i = call i16 @llvm.bswap.i16(i16 %0) #2
  store i16 %or130.i, i16* %out.6269.i, align 2
  br label %while.body117.i

fail.i:                                           ; preds = %while.body117.i
  ret void
}

; Function Attrs: nofree nosync nounwind readnone speculatable willreturn
declare i16 @llvm.bswap.i16(i16) #1

attributes #0 = { "target-features"="+neon,+v8a" }
attributes #1 = { nofree nosync nounwind readnone speculatable willreturn }
attributes #2 = { mustprogress nofree norecurse nosync nounwind readnone uwtable willreturn "frame-pointer"="non-leaf" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="generic" "target-features"="+neon,+v8a" }
```