bpf: Export btf_type_by_id() and bpf_log()

These symbols will be used in nf_conntrack.ko to support direct writes
to `nf_conn`.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Link: https://lore.kernel.org/r/3c98c19dc50d3b18ea5eca135b4fc3a5db036060.1662568410.git.dxu@dxuuu.xyz
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

kernel/bpf/btf.c

@@ -818,6 +818,7 @@ const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id)
 		return NULL;
 	return btf->types[type_id];
 }
+EXPORT_SYMBOL_GPL(btf_type_by_id);
 
 /*
  * Regular int is not a bit field and it must be either

kernel/bpf/verifier.c

@@ -370,6 +370,7 @@ __printf(2, 3) void bpf_log(struct bpf_verifier_log *log,
 	bpf_verifier_vlog(log, fmt, args);
 	va_end(args);
 }
+EXPORT_SYMBOL_GPL(bpf_log);
 
 static const char *ltrim(const char *s)
 {