Add MmServiceMgr_getId() to allow retrieval of service instance id

This commit adds MmServiceMgr_getId() to allow skeleton functions and service
deletion functions to retrieve the instance id it is acting upon. It also
reverts previous support for MmRpc_getId() and MmServiceMgr_register2.

Signed-off-by: VW <vwan@ti.com>
10 files changed