xdp: pass XDP flags into install handlers

Pass XDP flags to the xdp ndo.  This will allow drivers to look
at the mode flags and make decisions about offload.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -820,6 +820,7 @@ struct netdev_xdp {
 	union {
 		/* XDP_SETUP_PROG */
 		struct {
+			u32 flags;
 			struct bpf_prog *prog;
 			struct netlink_ext_ack *extack;
 		};