sctp: kill unused macros in head file

1. SCTP_CMD_NUM_VERBS,SCTP_CMD_MAX
These two macros have never been used for several years since v2.6.12-rc2.

2.sctp_port_rover,sctp_port_alloc_lock
The commit 063930 abandoned global variables of port_rover and port_alloc_lock,
but still keep two macros to refer to them.
So, remove them now.

commit 06393009
Author: Stephen Hemminger <shemminger@linux-foundation.org>
Date:   Wed Oct 10 17:30:18 2007 -0700

    [SCTP]: port randomization

Signed-off-by: Shan Wei <shanwei@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>