netdevsim: Don't accept device bound programs

Commit 2b3486bc ("bpf: Introduce device-bound XDP programs") introduced
device-bound programs by largely reusing existing offloading infrastructure.
This changed the semantics of 'prog->aux->offload' a bit. Now, it's non-NULL
for both offloaded and device-bound programs.

Instead of looking at 'prog->aux->offload' let's call bpf_prog_is_offloaded
which should be true iff the program is offloaded and not merely device-bound.

Fixes: 2b3486bc ("bpf: Introduce device-bound XDP programs")
Reported-by:  <syzbot+44c2416196b7c607f226@syzkaller.appspotmail.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Cc: Dipendra Khadka <kdipendra88@gmail.com>
Link: https://lore.kernel.org/bpf/20231114045453.1816995-2-sdf@google.com


Signed-off-by: Alexei Starovoitov <ast@kernel.org>