add needs_cpu_boost field to usb_class_driver and manage boost state in
usb_core, similar to needs_exclusive_storage.
Change-Id: Ieb0cd7bedda5b24bb0d209d5ce907db30f4815db
this is required to make hid endpoint of iap class driver work,
especially on ipodvideo(arc).
at least for arc, it is required to set mps as 64 instead of 512 on
highspeed, or some accessories ignore incoming hid reports.
Change-Id: I242060faced28a66204146a9c36ef10626d6d265
add class driver source files.
also register iap audio sink.
usbstack/iap/libiap directory is imported from libiap.
Change-Id: I776c5caec33fe9efadc448e2e3b37d500bf19c9f
