Fix handling of ECC public keys under MBEDTLS_PK_USE_PSA_EC_DATA

The test code to construct test keys and the implementation had matching
errors: both assumed that there was a PSA public key object. Fix this.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/suites/test_suite_pk.function b/tests/suites/test_suite_pk.function
index 3d7a179..efbe6b0 100644
--- a/tests/suites/test_suite_pk.function
+++ b/tests/suites/test_suite_pk.function
@@ -283,9 +283,7 @@
                                         PSA_KEY_USAGE_VERIFY_HASH);
                 psa_set_key_algorithm(&pub_attributes, PSA_ALG_ECDSA_ANY);
                 PSA_ASSERT(psa_destroy_key(pk->priv_id));
-                PSA_ASSERT(psa_import_key(&pub_attributes,
-                                          pk->pub_raw, pk->pub_raw_len,
-                                          &pk->priv_id));
+                pk->priv_id = MBEDTLS_SVC_KEY_ID_INIT;
 #else
                 mbedtls_ecp_keypair *ec = mbedtls_pk_ec_rw(*pk);
                 mbedtls_mpi_free(&ec->d);