ipvs: fixed sparse warning

Removed the following sparse warnings, wether CONFIG_SYSCTL
is defined or not:
*       warning: symbol 'ip_vs_control_net_init_sysctl' was not
	declared. Should it be static?
*       warning: symbol 'ip_vs_control_net_cleanup_sysctl' was
	not declared. Should it be static?

Signed-off-by: Claudiu Ghioc <claudiu.ghioc@gmail.com>
Signed-off-by: Simon Horman <horms@verge.net.au>