net: hinic: add missing destroy_workqueue in hinic_pf_to_mgmt_init

hinic_pf_to_mgmt_init misses destroy_workqueue in error path,
this patch fixes that.

Fixes: 6dbb8901 ("hinic: fix sending mailbox timeout in aeq event work")
Signed-off-by: Zheng Bin <zhengbin13@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>