Bluetooth: Implement Set ADV set random address

This basically sets the random address for the adv instance
Random address can be set only if the instance is created which
is done in Set ext adv param.

Random address and rpa expire timer and flags have been added
to adv instance which will be used when the respective
instance is scheduled.

This introduces a hci_get_random_address() which returns the
own address type and random address (rpa or nrpa) based
on the instance flags and hdev flags. New function is required
since own address type should be known before setting adv params
but address can be set only after setting params.

< HCI Command: LE Set Advertising Set Random Address (0x08|0x0035) plen 7
        Advertising handle: 0x00
        Advertising random address: 3C:8E:56:9B:77:84 (OUI 3C-8E-56)
> HCI Event: Command Complete (0x0e) plen 4
      LE Set Advertising Set Random Address (0x08|0x0035) ncmd 1
        Status: Success (0x00)

Signed-off-by: Jaganath Kanakkassery <jaganathx.kanakkassery@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>