Initialize platform in trng test

Add calls to `mbedtls_platform_setup()` and
`mbedtls_platform_terminate()` to the trng greentea test, to
initialize the hardware acceleration engines, in some platforms.

TESTS/mbed_hal/trng/main.cpp

@@ -43,6 +43,8 @@
 #include "base64b.h"
 #include "pithy.h"
 #include <stdio.h>
+#include "mbedtls/config.h"
+#include "mbedtls/platform.h"
 
 #if !DEVICE_TRNG
 #error [NOT_SUPPORTED] TRNG API not supported for this target
@@ -268,11 +270,17 @@ Specification specification(greentea_test_setup, cases, greentea_test_teardown_h
 
 int main()
 {
+    int ret = 0;
+#if defined(MBEDTLS_PLATFORM_C)
+    ret = mbedtls_platform_setup(NULL);
+#endif /* MBEDTLS_PLATFORM_C */
 #if (defined(TARGET_PSA) && defined(COMPONENT_PSA_SRV_IPC) && defined(MBEDTLS_PSA_CRYPTO_C))
     inject_entropy_for_psa();
 #endif
-    bool ret = !Harness::run(specification);
-
+    ret = !Harness::run(specification);
+#if defined(MBEDTLS_PLATFORM_C)
+    mbedtls_platform_teardown(NULL);
+#endif /* MBEDTLS_PLATFORM_C */
     return ret;
 }