Fix the name and the type of the argument for intrinisc
_mm256_broadcastsi128_si256 to align with the Intel documentation.

This fixes bug PR 16581 and rdar:14747994.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@188609 91177308-0d34-0410-b5e6-96231b3b80d8