create a random static address using random data

[paul-szczepanek-arm]

this is an edit to a PR

[ciarmcom]

@paul-szczepanek-arm, thank you for your changes.
@ARMmbed/mbed-os-maintainers please review.

[pan-]

Reading the data sheet, there's two registers that can be use to get an address:

• DeviceID: The register previously read
• DeviceAddress: Supposed to help the device address

I suggest we use one for the public address and the other for the random static address so we keep two addresses across reset.
This require update of the doInitialise function (see line 325). In general it would be a good thing to clarify public address provisioning and as many silicon vendor doesn't provide one.

[paul-szczepanek-arm]

I thought about that but there is no message in cordio to do that so that would be another modification to cordio

[paul-szczepanek-arm]

as for retaining the address, this will have the same address as it's seeded by the public address

Pull request has been modified.

[0xc0170]

A fix for PR to master from feature branch, will merge now as it is.