netfilter: nf_osf: move nf_osf_fingers to non-uapi header file

All warnings (new ones prefixed by >>):

>> ./usr/include/linux/netfilter/nf_osf.h:73: userspace cannot reference function or variable defined in the kernel

Fixes: f9324952 ("netfilter: nfnetlink_osf: extract nfnetlink_subsystem code from xt_osf.c")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/linux/netfilter/nf_osf.h

@@ -25,6 +25,8 @@ enum osf_fmatch_states {
 	FMATCH_OPT_WRONG,
 };
 
+extern struct list_head nf_osf_fingers[2];
+
 struct nf_osf_finger {
 	struct rcu_head			rcu_head;
 	struct list_head		finger_entry;

include/uapi/linux/netfilter/nf_osf.h

@@ -70,8 +70,6 @@ struct nf_osf_nlmsg {
 	struct tcphdr			tcp;
 };
 
-extern struct list_head nf_osf_fingers[2];
-
 /* Defines for IANA option kinds */
 enum iana_options {
 	OSFOPT_EOL = 0,		/* End of options */