Assign arguments of Neon intrinsic macros to local temporaries.

Assign arguments of Neon intrinsic macros to local temporaries.
Since we're casting them for the calls to the builtins, we need this to
make sure their types get checked in the same way they would if the intrinsics
were implemented as inline functions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120693 91177308-0d34-0410-b5e6-96231b3b80d8