[clang] [clang] fix half && bfloat16 convert node expr codegen (PR #89051)

[Matt Arsenault via cfe-commits]

arsenm wrote:

> > The vector tests should still be added
> 
> sorry. if i remove the change of the vector. i have to remove the testcase. because, for the current code convert between vector type of half and bfloat16, it has a bug. And it will be Assert "Invalid cast!""
> 

OK, LGTM with the else before return fixed. Can you handle the vector case in a follow up? 



https://github.com/llvm/llvm-project/pull/89051