[NET]: Fix potential stack overflow in net/core/utils.c

On High end systems (1024 or so cpus) this can potentially cause stack
overflow.  Fix the stack usage.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>