bpf: Fix a erroneous check after snprintf()

snprintf() does not return negative error code on error, it returns the
number of characters which *would* be generated for the given input.

Fix the error handling check.

Fixes: 57539b1c ("bpf: Enable annotating trusted nested pointers")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/393bdebc87b22563c08ace094defa7160eb7a6c0.1694190795.git.christophe.jaillet@wanadoo.frSigned-off-by: Alexei Starovoitov <ast@kernel.org>

kernel/bpf/btf.c

@@ -8501,7 +8501,7 @@ bool btf_nested_type_is_trusted(struct bpf_verifier_log *log,
 	tname = btf_name_by_offset(btf, walk_type->name_off);
 
 	ret = snprintf(safe_tname, sizeof(safe_tname), "%s%s", tname, suffix);
-	if (ret < 0)
+	if (ret >= sizeof(safe_tname))
 		return false;
 
 	safe_id = btf_find_by_name_kind(btf, safe_tname, BTF_INFO_KIND(walk_type->info));