bpf: Use kmemdup_array instead of kmemdup for multiple allocation

Let the kmemdup_array() take care about multiplication and possible
overflows.

Signed-off-by: Yu Jiaoliang <yujiaoliang@vivo.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20240821073709.4067177-1-yujiaoliang@vivo.com