liquidio: Using NULL instead of plain integer

Fixes the following sparse warnings:

drivers/net/ethernet/cavium/liquidio/lio_main.c:3068:23: warning:
 Using plain integer as NULL pointer
drivers/net/ethernet/cavium/liquidio/lio_main.c:2909:23: warning:
 Using plain integer as NULL pointer
drivers/net/ethernet/cavium/liquidio/cn23xx_vf_device.c:385:27: warning:
 Using plain integer as NULL pointer
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/cavium/liquidio/cn23xx_vf_device.c

@@ -382,7 +382,7 @@ void cn23xx_vf_ask_pf_to_do_flr(struct octeon_device *oct)
 	mbox_cmd.recv_len = 0;
 	mbox_cmd.recv_status = 0;
 	mbox_cmd.fn = NULL;
-	mbox_cmd.fn_arg = 0;
+	mbox_cmd.fn_arg = NULL;
 
 	octeon_mbox_write(oct, &mbox_cmd);
 }

drivers/net/ethernet/cavium/liquidio/lio_main.c

@@ -2906,7 +2906,7 @@ static int liquidio_set_vf_vlan(struct net_device *netdev, int vfidx,
 	    vfidx + 1; /* vfidx is 0 based, but vf_num (param2) is 1 based */
 	nctrl.ncmd.s.more = 0;
 	nctrl.iq_no = lio->linfo.txpciq[0].s.q_no;
-	nctrl.cb_fn = 0;
+	nctrl.cb_fn = NULL;
 	nctrl.wait_time = LIO_CMD_WAIT_TM;
 
 	octnet_send_nic_ctrl_pkt(oct, &nctrl);
@@ -3065,7 +3065,7 @@ static int liquidio_set_vf_link_state(struct net_device *netdev, int vfidx,
 	nctrl.ncmd.s.param2 = linkstate;
 	nctrl.ncmd.s.more = 0;
 	nctrl.iq_no = lio->linfo.txpciq[0].s.q_no;
-	nctrl.cb_fn = 0;
+	nctrl.cb_fn = NULL;
 	nctrl.wait_time = LIO_CMD_WAIT_TM;
 
 	octnet_send_nic_ctrl_pkt(oct, &nctrl);