net/sched: cls_api: remove redundant 0 check in tcf_qevent_init()

tcf_qevent_parse_block_index() never returns a zero block_index.
Therefore, it is unnecessary to check the value of block_index in
tcf_qevent_init().

Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Link: https://lore.kernel.org/r/20220901011617.14105-1-shaozhengchao@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>