fix build fail with MBEDTLS_DEPRECATED

When deprecated functions are allowed

Signed-off-by: Brett Warren <brett.warren@arm.com>
diff --git a/include/mbedtls/platform_util.h b/include/mbedtls/platform_util.h
index 26e628b..5d2fefc 100644
--- a/include/mbedtls/platform_util.h
+++ b/include/mbedtls/platform_util.h
@@ -50,6 +50,7 @@
 #define MBEDTLS_DEPRECATED_NUMERIC_CONSTANT( VAL )       \
     ( (mbedtls_deprecated_numeric_constant_t) ( VAL ) )
 #else /* MBEDTLS_DEPRECATED_WARNING */
+#define MBEDTLS_DEPRECATED
 #define MBEDTLS_DEPRECATED_STRING_CONSTANT( VAL ) VAL
 #define MBEDTLS_DEPRECATED_NUMERIC_CONSTANT( VAL ) VAL
 #endif /* MBEDTLS_DEPRECATED_WARNING */