bgpd: Remove trailing whitespaces from some header files

bgpd: Remove trailing whitespaces from some header files

This is annoying when editing a file and saving the file. IDEs like
VSCode can automatically remove trailing whitespaces, hence it would be better
having a clean code before pushing other changes.

I step onto this not the first time.

Signed-off-by: Donatas Abraitis <donatas.abraitis@gmail.com>