Only poison memory when buffer copying is enabled

Make sure that we don't enable memory poisoning when
MBEDTLS_PSA_COPY_CALLER_BUFFERS is disabled.

Signed-off-by: David Horstmann <david.horstmann@arm.com>
diff --git a/tests/src/helpers.c b/tests/src/helpers.c
index 843a9d4..36564fe 100644
--- a/tests/src/helpers.c
+++ b/tests/src/helpers.c
@@ -34,6 +34,7 @@
     int ret = 0;
 
 #if defined(MBEDTLS_TEST_HOOKS) && defined(MBEDTLS_PSA_CRYPTO_C) \
+    && defined(MBEDTLS_PSA_COPY_CALLER_BUFFERS) \
     && defined(MBEDTLS_TEST_MEMORY_CAN_POISON)
     mbedtls_poison_test_hooks_setup();
 #endif
@@ -59,6 +60,7 @@
 void mbedtls_test_platform_teardown(void)
 {
 #if defined(MBEDTLS_TEST_HOOKS) && defined(MBEDTLS_PSA_CRYPTO_C) \
+    && defined(MBEDTLS_PSA_COPY_CALLER_BUFFERS) \
     &&  defined(MBEDTLS_TEST_MEMORY_CAN_POISON)
     mbedtls_poison_test_hooks_teardown();
 #endif