Revert "[CodeGenPrepare] Move sign/zero extensions near loads using type promotion."

This reverts commit r224351. It causes assertion failures when building
ICU.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224397 91177308-0d34-0410-b5e6-96231b3b80d8
PR21875: codegen for non-type template parameters of nullptr_t type

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224399 91177308-0d34-0410-b5e6-96231b3b80d8