bpf: report offload info to user space

bpf: report offload info to user space

Extend struct bpf_prog_info to contain information about program
being bound to a device.  Since the netdev may get destroyed while
program still exists we need a flag to indicate the program is
loaded for a device, even if the device is gone.

Signed-off-by: Jakub Kicinski <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Reviewed-by: Quentin Monnet <[email protected]>
Signed-off-by: David S. Miller <[email protected]>