[PATCH bpf] bpf: Fix build in minimal configurations

[Alexei Starovoitov <ast@kernel.org>]

Some kconfigs can have BPF enabled without a single valid program type.
In such configurations the build will fail with:
./kernel/bpf/btf.c:3466:1: error: empty enum is invalid

Fix it by adding unused value to the enum.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 kernel/bpf/btf.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index bd5e11881ba3..7d40da240891 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3463,6 +3463,7 @@ enum {
 	__ctx_convert##_id,
 #include <linux/bpf_types.h>
 #undef BPF_PROG_TYPE
+	__ctx_convert_unused, /* to avoid empty enum in extreme .config */
 };
 static u8 bpf_ctx_convert_map[] = {
 #define BPF_PROG_TYPE(_id, _name, prog_ctx_type, kern_ctx_type) \
-- 
2.23.0