RDMA/hns: remove set but not used variable 'irq_num'

RDMA/hns: remove set but not used variable 'irq_num'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/infiniband/hw/hns/hns_roce_hw_v2.c: In function hns_roce_v2_cleanup_eq_table:
drivers/infiniband/hw/hns/hns_roce_hw_v2.c:5920:6:
 warning: variable irq_num set but not used [-Wunused-but-set-variable]

It is not used since
commit 33db6f94847c ("RDMA/hns: Refactor eq table init for hip08")

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20190731073748.17664-1-yuehaibing@huawei.com
Signed-off-by: Doug Ledford <dledford@redhat.com>