Revert "netprio_cgroup: make local table static"

This reverts commit 763eff57.

It causes build regressions, as per Stephen Rothwell:

====================
After merging the final tree, today's linux-next build (powerpc
allyesconfig) failed like this:

net/core/netprio_cgroup.c:250:29: error: static declaration of 'net_prio_subsys' follows non-static declaration
include/linux/cgroup_subsys.h:71:1: note: previous declaration of 'net_prio_subsys' was here
====================
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/netprio_cgroup.c

@@ -247,7 +247,7 @@ static struct cftype ss_files[] = {
 	{ }	/* terminate */
 };
 
-static struct cgroup_subsys net_prio_subsys = {
+struct cgroup_subsys net_prio_subsys = {
 	.name		= "net_prio",
 	.css_alloc	= cgrp_css_alloc,
 	.css_online	= cgrp_css_online,