Bluetooth: Controller: Kconfig option to set public address

Added Kconfig option to be able set public address. Seems
conformance testers look for valid public address.

Change-Id: I2c4f702117f99a42c9eef0133b46556a1c6d1496
Signed-off-by: Vinayak Chettimada <vinayak.kariappa.chettimada@nordicsemi.no>