net core: Remove unneded creation of an empty net/core sysctl directory

On the next line we register the net_core_table in net/core which
creates the directory and ensures it exists.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: David S. Miller <davem@davemloft.net>