Change Neon VLDn intrinsics to return multiple values instead of really

Change Neon VLDn intrinsics to return multiple values instead of really
wide vectors.  Likewise, change VSTn intrinsics to take separate arguments
for each vector in a multi-vector struct.  Adjust tests accordingly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@77468 91177308-0d34-0410-b5e6-96231b3b80d8