Include psa_crypto_helpers.h in helpers.function

Include psa_crypto_helpers.h automatically if MBEDTLS_PSA_CRYPTO_C is
enabled, like helpers.h is included automatically.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/suites/helpers.function b/tests/suites/helpers.function
index aafcf5c..3a9c426 100644
--- a/tests/suites/helpers.function
+++ b/tests/suites/helpers.function
@@ -5,6 +5,9 @@
 #include <test/macros.h>
 #include <test/helpers.h>
 #include <test/random.h>
+#if defined(MBEDTLS_PSA_CRYPTO_C)
+#include <test/psa_crypto_helpers.h>
+#endif
 
 #include <stdlib.h>