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

This patch adds the relevant callback prototyps for Set Idle and
Get Idle which is used for setting idle time on HID devices.

Change-Id: I4c528a510edd847bc6121ce0b875ae313f090b9c
CRs-Fixed: 522511
Merge "Bluetooth: HID: Add support for Set Idle and Get Idle commands" into jb4.3