f_bpf: communicate ifindex for eBPF offload

f_bpf: communicate ifindex for eBPF offload

Split parsing and loading of the eBPF program and if skip_sw is set
load the program for ifindex, to which the qdisc is attached.

Note that the ifindex will be ignored for programs which are already
loaded (e.g. when using pinned programs), but in that case we just
trust the user knows what he's doing.  Hopefully we will get extack
soon in the driver to help debugging this case.

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