Add requested montgomery curve tests

* Add tests to validate MSB not ok for Curve25519 and
  Curve448.
* Add a test to generate key for for Curve448.

Signed-off-by: Archana <archana.madhavan@silabs.com>
diff --git a/tests/suites/test_suite_psa_crypto.data b/tests/suites/test_suite_psa_crypto.data
index defb3f4..6eca2f7 100644
--- a/tests/suites/test_suite_psa_crypto.data
+++ b/tests/suites/test_suite_psa_crypto.data
@@ -3783,6 +3783,10 @@
 depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR:PSA_WANT_ECC_MONTGOMERY_255
 generate_key:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):255:PSA_KEY_USAGE_EXPORT | PSA_KEY_USAGE_DERIVE:PSA_ALG_ECDH:PSA_SUCCESS:0
 
+PSA generate key: ECC, Curve448, good
+depends_on:PSA_WANT_ALG_ECDH:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR:PSA_WANT_ECC_MONTGOMERY_448
+generate_key:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_MONTGOMERY):448:PSA_KEY_USAGE_EXPORT | PSA_KEY_USAGE_DERIVE:PSA_ALG_ECDH:PSA_SUCCESS:0
+
 PSA generate key: RSA, default e
 generate_key_rsa:512:"":PSA_SUCCESS