Fix PR15267

Fix PR15267

- When extloading from a vector with non-byte-addressable element, e.g.
  <4 x i1>, the current logic breaks. Extend the current logic to
  fix the case where the element type is not byte-addressable by loading
  all bytes, bit-extracting/packing each element.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175642 91177308-0d34-0410-b5e6-96231b3b80d8