Add updateable association to active BMC FW object

Add 'updateable' association to the active BMC
firmware version object. This 'updateable' association
can be used to mark all the firmware components
which can be programmable from BMC interfaces like
Redfish.

Tested:
 - Able to query the updateable endpoint objects.
Req:
 busctl call xyz.openbmc_project.ObjectMapper
 /xyz/openbmc_project/software/updateable
 org.freedesktop.DBus.Properties Get ss
 xyz.openbmc_project.Association endpoints

Res:
 v as 1 "/xyz/openbmc_project/software/1201fc36"

- Get on FirmwareInventory shows correct value
  for 'Updateable' property. Redfish support is
  added as new commit.

 URI: /redfish/v1/UpdateService/FirmwareInventory/1201fc36
 Res: Can see "Updateable": true output

Change-Id: Id74a134dacdea86399d10fbe0a4b0e62728d1cf4
Signed-off-by: AppaRao Puli <apparao.puli@linux.intel.com>
4 files changed