test_suite_x509parse.function improvement

as suggested in
https://github.com/ARMmbed/mbedtls/pull/3419#discussion_r441433697

also removed two no longer necessary void casts

Signed-off-by: Nicola Di Lieto <nicola.dilieto@gmail.com>
diff --git a/tests/suites/test_suite_x509parse.function b/tests/suites/test_suite_x509parse.function
index a72532f..9cac2ec 100644
--- a/tests/suites/test_suite_x509parse.function
+++ b/tests/suites/test_suite_x509parse.function
@@ -306,8 +306,6 @@
                       int critical, const unsigned char *cp, const unsigned char *end )
 {
     ( void ) crt;
-    ( void ) cp;
-    ( void ) end;
     ( void ) critical;
     mbedtls_x509_buf *new_oid = (mbedtls_x509_buf *)p_ctx;
     if( oid->tag == MBEDTLS_ASN1_OID &&
@@ -352,6 +350,9 @@
                                               MBEDTLS_ASN1_OID ) ) != 0 )
                 return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
 
+            /*
+             * Recognize exclusively the policy with OID 1
+             */
             if( len != 1 || *p[0] != 1 )
                 parse_ret = MBEDTLS_ERR_X509_FEATURE_UNAVAILABLE;