This is the follow up of :

https://developer.trustedfirmware.org/T501

The existing method looks a bit complicate, let's think about a new way to fulfil:

• 1~INT32_MAX as valid handle value.
• Need to reserve 1 bit for indicating default/non-default handle type.
• Do not return direct secure address to the client.
• Nice to have: Do not return used handle value to the client in a short period. (The short here may be confusing, for me, just prove a keep-allocating/free in number of times would not get the same handle is OKAY)