tools: bpftool: deal with options upfront

Remove options (in getopt() sense, i.e. starting with a dash like
-n or --NAME) while parsing arguments for bash completions.  This
allows us to refer to position-dependent parameters better, and
complete options at any point.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>