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/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 1781d99..482fa57 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -525,7 +525,7 @@
 
 		genl_unlock();
 		err = netlink_dump_start(net->genl_sock, skb, nlh,
-					 ops->dumpit, ops->done);
+					 ops->dumpit, ops->done, 0);
 		genl_lock();
 		return err;
 	}