Initialize psa_crypto in ssl test

Call `psa_crypto_init()` in `tls_prf` ssl test in case
`MBEDTLS_USE_PSA_CRYPTO` is defined since tls_prf may use psa crypto.
diff --git a/tests/suites/test_suite_ssl.function b/tests/suites/test_suite_ssl.function
index 69b9778..ecf186e 100644
--- a/tests/suites/test_suite_ssl.function
+++ b/tests/suites/test_suite_ssl.function
@@ -552,6 +552,10 @@
     if( output == NULL )
         goto exit;
 
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+    TEST_ASSERT( psa_crypto_init() == 0 );
+#endif
+
     TEST_ASSERT( mbedtls_ssl_tls_prf( type, secret->x, secret->len,
                                       label, random->x, random->len,
                                       output, result_hex_str->len ) == exp_ret );