samples/bpf: test_cgrp2_sock2: fix an off by one

"prog_cnt" is the number of elements which are filled out in prog_fd[]
so the test should be >= instead of >.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>