Fix the build without MBEDTLS_PLATFORM_C

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/programs/test/benchmark.c b/programs/test/benchmark.c
index d63009a..7845bee 100644
--- a/programs/test/benchmark.c
+++ b/programs/test/benchmark.c
@@ -50,18 +50,14 @@
 #include MBEDTLS_CONFIG_FILE
 #endif
 
-#if defined(MBEDTLS_PLATFORM_C)
 #include "mbedtls/platform.h"
-#else
+#if !defined(MBEDTLS_PLATFORM_C)
 #include <stdio.h>
 #include <stdlib.h>
 #define mbedtls_exit       exit
 #define mbedtls_printf     printf
-#define mbedtls_snprintf   snprintf
 #define mbedtls_free       free
 #define mbedtls_exit            exit
-#define MBEDTLS_EXIT_SUCCESS    EXIT_SUCCESS
-#define MBEDTLS_EXIT_FAILURE    EXIT_FAILURE
 #endif
 
 #if !defined(MBEDTLS_TIMING_C)