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/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index 6ffe94c..5ff4765 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -871,7 +871,7 @@
 		}
 
 		return netlink_dump_start(idiagnl, skb, nlh,
-					  inet_diag_dump, NULL);
+					  inet_diag_dump, NULL, 0);
 	}
 
 	return inet_diag_get_exact(skb, nlh);