Bluetooth: Controller: Add Kconfig range check for public address

Bluetooth device address is 48-bit, added Kconfig range
field to restrict input to 48-bit hexadecimal value.

Change-id: I650343eab5809535137e164e783c9dd4f3e2a6f2
Signed-off-by: Vinayak Chettimada <vinayak.kariappa.chettimada@nordicsemi.no>