[refactoring][bssl] Move check_int_result to util module

To facilitate its reuse in other modules such as hkdf and aead
later.

Test: atest libbssl_avf_nostd.test
Bug: 302286887
Change-Id: I5373047dcd6c264eee872d46c616cd1c2b475192
diff --git a/libs/bssl/src/lib.rs b/libs/bssl/src/lib.rs
index 500419b..1824080 100644
--- a/libs/bssl/src/lib.rs
+++ b/libs/bssl/src/lib.rs
@@ -22,6 +22,7 @@
 mod digest;
 mod ec_key;
 mod hmac;
+mod util;
 
 pub use bssl_avf_error::{ApiName, Error, Result};
 pub use cbb::CbbFixed;