octeontx2-pf: mcs: fix possible memory leak in otx2_probe()

In error path after calling cn10k_mcs_init(), cn10k_mcs_free() need
be called to avoid memory leak.

Fixes: c54ffc73

 ("octeontx2-pf: mcs: Introduce MACSEC hardware offloading")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>