lwt_bpf: bpf_lwt_prog_cmp() can be static

Fixes the following sparse warning:

net/core/lwt_bpf.c:355:5: warning:
 symbol 'bpf_lwt_prog_cmp' was not declared. Should it be static?
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Acked-by: NDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/lwt_bpf.c

@@ -352,7 +352,7 @@ static int bpf_encap_nlsize(struct lwtunnel_state *lwtstate)
 	       0;
 }
 
-int bpf_lwt_prog_cmp(struct bpf_lwt_prog *a, struct bpf_lwt_prog *b)
+static int bpf_lwt_prog_cmp(struct bpf_lwt_prog *a, struct bpf_lwt_prog *b)
 {
 	/* FIXME:
 	 * The LWT state is currently rebuilt for delete requests which