Revert "Implement AArch64 vector load/store multiple N-element structure class SIMD(lselem). "

This reverts commit r192351. The LLVM side broke the build and the Clang tests
will inevitably fail without it.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@192356 91177308-0d34-0410-b5e6-96231b3b80d8