rtnetlink: Compute and store minimum ifinfo dump size

The message size allocated for rtnl ifinfo dumps was limited to
a single page.  This is not enough for additional interface info
available with devices that support SR-IOV and caused a bug in
which VF info would not be displayed if more than approximately
40 VFs were created per interface.

Implement a new function pointer for the rtnl_register service that will
calculate the amount of data required for the ifinfo dump and allocate
enough data to satisfy the request.

Signed-off-by: Greg Rose <gregory.v.rose@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/infiniband/core/netlink.c b/drivers/infiniband/core/netlink.c
index 4a5abaf..9227f4a 100644
--- a/drivers/infiniband/core/netlink.c
+++ b/drivers/infiniband/core/netlink.c
@@ -148,7 +148,7 @@
 				return -EINVAL;
 			return netlink_dump_start(nls, skb, nlh,
 						  client->cb_table[op].dump,
-						  NULL);
+						  NULL, 0);
 		}
 	}