samples/bpf: Fix the error return code of xdp_redirect's main()

[ Upstream commit 7c6090ee2a7b3315410cfc83a94c3eb057407b25 ]

Fix to return a negative error code from the error handling
case instead of 0, as done elsewhere in this function.

If bpf_map_update_elem() failed, main() should return a negative error.

Fixes: 832622e ("xdp: sample program for new bpf_redirect helper")
Signed-off-by: Wang Hai <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]
Signed-off-by: Sasha Levin <[email protected]>

samples/bpf/xdp_redirect_user.c

@@ -139,5 +139,5 @@ int main(int argc, char **argv)
 	poll_stats(2, ifindex_out);
 
 out:
-	return 0;
+	return ret;
 }