Define MBEDTLS_DECLARE_PRIVATE_IDENTIFIERS in every sample program

Add #define MBEDTLS_DECLARE_PRIVATE_IDENTIFIERS to every sample program
before the first include so that mbedtls doesn't break with future
privatization work.

Signed-off-by: Felix Conway <felix.conway@arm.com>
diff --git a/programs/cipher/cipher_aead_demo.c b/programs/cipher/cipher_aead_demo.c
index 83fcce5..533af34 100644
--- a/programs/cipher/cipher_aead_demo.c
+++ b/programs/cipher/cipher_aead_demo.c
@@ -31,6 +31,8 @@
 /* First include Mbed TLS headers to get the Mbed TLS configuration and
  * platform definitions that we'll use in this program. Also include
  * standard C headers for functions we'll use here. */
+#define MBEDTLS_DECLARE_PRIVATE_IDENTIFIERS
+
 #include "mbedtls/build_info.h"
 
 #include "mbedtls/cipher.h"