IB/IPoIB: Fix kernel panic on multicast flow

ipoib_mcast_restart_task calls ipoib_mcast_remove_list with the
parameter mcast->dev. That mcast is a temporary (used as an iterator)
variable that may be uninitialized.
There is no need to send the variable dev to the function, as each mcast
has its dev as a member in the mcast struct.

This causes the next panic:
RIP: 0010: ipoib_mcast_leave+0x6d/0xf0 [ib_ipoib]
RSP: 0018: EFLAGS: 00010246
RAX: f0201 RBX: 24e00 RCX: 00000
....
....
Stack:
Call Trace:
	ipoib_mcast_remove_list+0x3a/0x70 [ib_ipoib]
	ipoib_mcast_restart_task+0x3bb/0x520 [ib_ipoib]
	process_one_work+0x164/0x470
	worker_thread+0x11d/0x420
	...

Fixes: 5a0e81f6f483 ('IB/IPoIB: factor out common multicast list removal code')
Signed-off-by: Erez Shitrit <erezsh@mellanox.com>
Reported-by: Doron Tsur <doront@mellanox.com>
Reviewed-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
diff --git a/drivers/infiniband/ulp/ipoib/ipoib_main.c b/drivers/infiniband/ulp/ipoib/ipoib_main.c
index 0a93cb2..25509bb 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_main.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c
@@ -1150,7 +1150,6 @@
 	unsigned long flags;
 	int i;
 	LIST_HEAD(remove_list);
-	struct net_device *dev = priv->dev;
 
 	if (test_bit(IPOIB_STOP_NEIGH_GC, &priv->flags))
 		return;
@@ -1196,7 +1195,7 @@
 
 out_unlock:
 	spin_unlock_irqrestore(&priv->lock, flags);
-	ipoib_mcast_remove_list(dev, &remove_list);
+	ipoib_mcast_remove_list(&remove_list);
 }
 
 static void ipoib_reap_neigh(struct work_struct *work)