qlcnic: Fix NULL pointer dereference in VF probe path.

o Check for non-NULL set_mac_filter_count function pointer
  before calling it fixes the panic.

This patch fixes regression introduced by patch
"qlcnic: Secondary unicast MAC address support." with
commit id 168e4fb54c11865668ad50eff81b5f2729e0e0f4.

Signed-off-by: Sucheta Chakraborty <sucheta.chakraborty@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/qlogic/qlcnic/qlcnic.h

@@ -1869,7 +1869,8 @@ static inline void qlcnic_free_mac_list(struct qlcnic_adapter *adapter)
 
 static inline void qlcnic_set_mac_filter_count(struct qlcnic_adapter *adapter)
 {
-	adapter->ahw->hw_ops->set_mac_filter_count(adapter);
+	if (adapter->ahw->hw_ops->set_mac_filter_count)
+		adapter->ahw->hw_ops->set_mac_filter_count(adapter);
 }
 
 static inline void qlcnic_dev_request_reset(struct qlcnic_adapter *adapter,