ipvs: ip_vs_ftp: local functions should not be exposed globally

Functions not referenced outside of a source file should be marked
static to prevent it from being exposed globally.

This quiets the sparse warnings:

warning: symbol 'ip_vs_ftp_init' was not declared. Should it be static?
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Simon Horman <horms@verge.net.au>

net/netfilter/ipvs/ip_vs_ftp.c

@@ -485,7 +485,7 @@ static struct pernet_operations ip_vs_ftp_ops = {
 	.exit = __ip_vs_ftp_exit,
 };
 
-int __init ip_vs_ftp_init(void)
+static int __init ip_vs_ftp_init(void)
 {
 	int rv;