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

This patch provides an interface for application to send Set Idle
and Get Idle commands to remote HID Device. Support for these
two commands was missing from exisitng code, so existing code
design is reused to add support for these two commands.

Change-Id: I548362cc328498920b2dae740f1a76b2cc2d6a67
CRs-Fixed: 522511
(cherry picked from commit e98b0a3118b9c7a72f8e65e7e080259e6f032db8)
(cherry picked from commit 14fd26713fa406174f6d770506708dbbfd8c2a2e)
(cherry picked from commit 3a40bbc088c1c09fba649d40a7670760c17d5a38)