iwlwifi: use bus_get_hw_id for IWL_TM_CMD_APP2DEV_GET_DEVICE_ID

instead of doing all the work in IWL_TM_CMD_APP2DEV_GET_DEVICE_ID, just use
the information from bus_get_hw_id()

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>