octeontx2-pf: Fix missing spin_lock_init() in otx2_tc_add_flow()

The driver allocates the spinlock but not initialize it.
Use spin_lock_init() on it to initialize it correctly.

Fixes: d8ce30e0 ("octeontx2-pf: add tc flower stats handler for hw offloads")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>