Replace malloc with calloc

- platform layer currently broken (not adapted yet)
- memmory_buffer_alloc too
diff --git a/tests/suites/main_test.function b/tests/suites/main_test.function
index c4ce580..ecd5182 100644
--- a/tests/suites/main_test.function
+++ b/tests/suites/main_test.function
@@ -6,7 +6,7 @@
 #include <stdio.h>
 #define mbedtls_exit       exit
 #define mbedtls_free       free
-#define mbedtls_malloc     malloc
+#define mbedtls_calloc    calloc
 #define mbedtls_fprintf    fprintf
 #define mbedtls_printf     printf
 #endif