Use the existing definition of MBEDTLS_TEST_HAVE_ASAN

A definition now exists in tests/helpers.h, which is a better place.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/include/test/memory.h b/tests/include/test/memory.h
index a10e985..8080f98 100644
--- a/tests/include/test/memory.h
+++ b/tests/include/test/memory.h
@@ -23,14 +23,6 @@
  *
  * Currently, only Asan (Address Sanitizer) is supported.
  */
-#if defined(__SANITIZE_ADDRESS__)
-#  define MBEDTLS_TEST_HAVE_ASAN
-#endif
-#if defined(__has_feature)
-#  if __has_feature(address_sanitizer)
-#    define MBEDTLS_TEST_HAVE_ASAN
-#  endif
-#endif
 #if defined(MBEDTLS_TEST_HAVE_ASAN)
 #  define MBEDTLS_TEST_MEMORY_CAN_POISON
 #endif