netfilter: uapi: fix linux/netfilter/nf_osf.h userspace compilation errors

Move inclusion of <linux/ip.h> and <linux/tcp.h> from
linux/netfilter/xt_osf.h to linux/netfilter/nf_osf.h to fix
the following linux/netfilter/nf_osf.h userspace compilation errors:

/usr/include/linux/netfilter/nf_osf.h:59:24: error: 'MAX_IPOPTLEN' undeclared here (not in a function)
  struct nf_osf_opt opt[MAX_IPOPTLEN];
/usr/include/linux/netfilter/nf_osf.h:64:17: error: field 'ip' has incomplete type
  struct iphdr   ip;
/usr/include/linux/netfilter/nf_osf.h:65:18: error: field 'tcp' has incomplete type
  struct tcphdr   tcp;

Fixes: bfb15f2a

 ("netfilter: extract Passive OS fingerprint infrastructure from xt_osf")
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>