selftests/bpf: add netdevsim to config

BPF offload tests (test_offload.py) will require netdevsim
to be built, add it to config.

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

tools/testing/selftests/bpf/config

@@ -4,3 +4,4 @@ CONFIG_NET_CLS_BPF=m
 CONFIG_BPF_EVENTS=y
 CONFIG_TEST_BPF=m
 CONFIG_CGROUP_BPF=y
+CONFIG_NETDEVSIM=m