Fix usage of ASSERT_ALLOC()

The second argument is the number of elements of the type the first
argument is pointing to, so we shouldn't be using sizeof there.

This was resulting in overly large allocations.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>

tests/suites/test_suite_asn1parse.function

@@ -779,7 +779,7 @@ void free_named_data_list( int length )
     for( i = 0; i < length; i++ )
     {
         mbedtls_asn1_named_data *new = NULL;
-        ASSERT_ALLOC( new, sizeof( mbedtls_asn1_named_data ) );
+        ASSERT_ALLOC( new, 1 );
         new->next = head;
         head = new;
     }