bpf: Fix unused variable warning

Hiding the only using of bpf_link_type_strs[] in an #ifdef causes
an unused-variable warning:

kernel/bpf/syscall.c:2280:20: error: 'bpf_link_type_strs' defined but not used [-Werror=unused-variable]
 2280 | static const char *bpf_link_type_strs[] = {

Move the definition into the same #ifdef.

Fixes: f2e10bff ("bpf: Add support for BPF_OBJ_GET_INFO_BY_FD for bpf_link")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200429132217.1294289-1-arnd@arndb.de

kernel/bpf/syscall.c

@@ -2271,6 +2271,7 @@ static int bpf_link_release(struct inode *inode, struct file *filp)
 	return 0;
 }
 
+#ifdef CONFIG_PROC_FS
 #define BPF_PROG_TYPE(_id, _name, prog_ctx_type, kern_ctx_type)
 #define BPF_MAP_TYPE(_id, _ops)
 #define BPF_LINK_TYPE(_id, _name) [_id] = #_name,
@@ -2282,7 +2283,6 @@ static const char *bpf_link_type_strs[] = {
 #undef BPF_MAP_TYPE
 #undef BPF_LINK_TYPE
 
-#ifdef CONFIG_PROC_FS
 static void bpf_link_show_fdinfo(struct seq_file *m, struct file *filp)
 {
 	const struct bpf_link *link = filp->private_data;