include private pk.h internally

Signed-off-by: Ben Taylor <ben.taylor@linaro.org>
diff --git a/tests/suites/test_suite_x509parse.function b/tests/suites/test_suite_x509parse.function
index 4f0605c..079dca4 100644
--- a/tests/suites/test_suite_x509parse.function
+++ b/tests/suites/test_suite_x509parse.function
@@ -11,6 +11,9 @@
 #include "mbedtls/base64.h"
 #include "mbedtls/error.h"
 #include "mbedtls/pk.h"
+#if defined(MBEDTLS_PK_HAVE_PRIVATE_HEADER)
+#include <mbedtls/private/pk_private.h>
+#endif /* MBEDTLS_PK_HAVE_PRIVATE_HEADER */
 #include "mbedtls/asn1.h"
 #include "mbedtls/asn1write.h"
 #include "string.h"