module: Do not access sig_enforce directly

Call is_module_sig_enforced() instead.

Signed-off-by: Jia Zhang <zhang.jia@linux.alibaba.com>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
diff --git a/kernel/module.c b/kernel/module.c
index a6e43a5..f695474 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2785,7 +2785,7 @@
 	}
 
 	/* Not having a signature is only an error if we're strict. */
-	if (err == -ENOKEY && !sig_enforce)
+	if (err == -ENOKEY && !is_module_sig_enforced())
 		err = 0;
 
 	return err;