[AArch64] Narrow arguments passed in wrong position on the stack in
big-endian mode.

Patch by Asiri Rathnayake.

Differential Revision: http://reviews.llvm.org/D4922

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215716 91177308-0d34-0410-b5e6-96231b3b80d8