bpf: Remove unused vairable 'bpf_xdp_link_lops'

kernel/bpf/syscall.c:2263:34: warning: 'bpf_xdp_link_lops' defined but not used [-Wunused-const-variable=]
 static const struct bpf_link_ops bpf_xdp_link_lops;
                                  ^~~~~~~~~~~~~~~~~

commit 70ed506c3b ("bpf: Introduce pinnable bpf_link abstraction")
involded this unused variable, remove it.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200326031613.19372-1-yuehaibing@huawei.com

kernel/bpf/syscall.c

@@ -2252,7 +2252,6 @@ static int bpf_link_release(struct inode *inode, struct file *filp)
 #ifdef CONFIG_PROC_FS
 static const struct bpf_link_ops bpf_raw_tp_lops;
 static const struct bpf_link_ops bpf_tracing_link_lops;
-static const struct bpf_link_ops bpf_xdp_link_lops;
 
 static void bpf_link_show_fdinfo(struct seq_file *m, struct file *filp)
 {