le_device_db_init() function

Note: LE Device DB for pure LE Peripherals is not required if only LE Legacy Pairing without signed writes is used Per bonded device: - it stores the Identity Resolving Key (IRK) and its address to resolve private addresses - it stores the LTK + EDIV, RAND. EDIV + RAND allows a LE Peripheral to reconstruct the LTK - it stores the Connection Signature Resolving Key (CSRK) and the last used counter. The CSRK is used to generate the signatur on the remote device and is needed to verify the signature itself The Counter is necessary to prevent reply attacks init