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
(cherry picked from commit d733cfe1637fa61e2823a50440f5adbd26bc12a9)
(cherry picked from commit 27ad0703c8b8a0ce129cf46e61d1410406fd3f3c)
(cherry picked from commit 60f843ee8e3c4ef097394e2483c2c80922c182e2)