Remove platform devices for USB functions

With the new USB composite framework, USB functions need
not to be registered as platform devices.
Register only android_composite device as platform device
which is used to pass update_pid_serial_number function
callback used by DIAG.

Change-Id: Ice9f964693b7fe80b263b57b9f277d994b950906
Merge "Remove platform devices for USB functions" into cm-10.1