Comments in the verifier refer to free_bpf_prog_info() which
seems to have never existed in tree.  Replace it with
free_used_maps().
Signed-off-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: NQuentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>