Fix cross-platform compilation issue

Signed-off-by: Jethro Beekman <[email protected]>

tests/suites/test_suite_pem.function

@@ -35,7 +35,7 @@ exit:
 /* BEGIN_CASE depends_on:MBEDTLS_PEM_WRITE_C */
 void mbedtls_pem_write_buffer_lengths()
 {
-    unsigned char data[256] = {};
+    unsigned char data[256] = { 0 };
     unsigned char buf[1024];
     size_t olen_needed, olen;
     int ret;