[clang] [NFC][Clang] Move set functions out BranchProtectionInfo. (PR #98451)

[Daniel Kiss via cfe-commits]

DanielKristofKiss wrote:

 #83277 needs the `setBranchProtectionFnAttributes` function but that call is from a static function so let's make it static.

https://github.com/llvm/llvm-project/pull/98451