Bluetooth: HID: Add support for Set Idle and Get Idle commands

This patch adds support for sending set idle and get idle commands to
remote HID device, on receiving the function call from upper layers.
Also on reception of get idle time from remote device, upper layers
are infrmed using registered callback.

Change-Id: I14bc2dc349354fd87ef8aba25357514398532e87
CRs-Fixed: 522511