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/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index c658cb3..0256b8a 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -2299,7 +2299,8 @@
 		if (link->dump == NULL)
 			return -EINVAL;
 
-		return netlink_dump_start(net->xfrm.nlsk, skb, nlh, link->dump, link->done);
+		return netlink_dump_start(net->xfrm.nlsk, skb, nlh,
+					  link->dump, link->done, 0);
 	}
 
 	err = nlmsg_parse(nlh, xfrm_msg_min[type], attrs, XFRMA_MAX,