Fix types in documentation.

The examples were using f32, but the IR type is called float

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212675 91177308-0d34-0410-b5e6-96231b3b80d8
R600/SI: Add support for llvm.convert.{to|from}.fp16

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212676 91177308-0d34-0410-b5e6-96231b3b80d8