key_ladder_demo: Initialize additional data to all zeroes

The header structure was initialized only field by
field. This does not initialized the padding bytes
and MemSan was complaining with use of
uninitialized data in test_memsan all.sh component.

Signed-off-by: Ronald Cron <ronald.cron@arm.com>

programs/psa/key_ladder_demo.c

@@ -392,6 +392,7 @@ static psa_status_t wrap_data(const char *input_file_name,
     input_file = NULL;
 
     /* Construct a header. */
+    memset(&header, 0, sizeof(header));
     memcpy(&header.magic, WRAPPED_DATA_MAGIC, WRAPPED_DATA_MAGIC_LENGTH);
     header.ad_size = sizeof(header);
     header.payload_size = input_size;