Merge branch 'bpf-bpftool-makefile-cleanups'

Quentin Monnet says:

====================
First patch of this series cleans up the two Makefiles (Makefile and
Documentation/Makefile) and make their contents more consistent.

The second one add "uninstall" and "doc-uninstall" targets, to remove
files previously installed on the system with "install" and "doc-install"
targets.
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>