mirror: Update .gitignore files

Since the current repository has a layout that differs from the
tools/bpf/bpftool/ directory from the kernel, a few entries in the
.gitignore files may require some adjustements. In particular:

- Move the entry for generated man pages to a dedicated .gitignore under
  docs/
- Add an entry for the .o object files, which are covered by a
  higher-level .gitignore in the kernel repository.

Signed-off-by: Quentin Monnet <quentin@isovalent.com>
3 files changed