Introduce PSA_KEY_HANDLE_INIT macro

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/tests/suites/test_suite_pk.function b/tests/suites/test_suite_pk.function
index c6041b2..22bf0e7 100644
--- a/tests/suites/test_suite_pk.function
+++ b/tests/suites/test_suite_pk.function
@@ -151,7 +151,7 @@
 
     TEST_ASSERT( psa_crypto_init( ) == PSA_SUCCESS );
 
-    TEST_ASSERT( mbedtls_pk_setup_opaque( &pk, 0 ) ==
+    TEST_ASSERT( mbedtls_pk_setup_opaque( &pk, PSA_KEY_HANDLE_INIT ) ==
                  MBEDTLS_ERR_PK_BAD_INPUT_DATA );
 
     mbedtls_pk_free( &pk );