[usb-test][fx3] Support fx3 second stage bootloader.

The default fx3 bootloader has an issue where if you reboot,
it enters low-power suspend mode and will not wake up again.
The second stage bootloader is recommended by Cypress as a workaround.

When the fx3 device is running the second stage bootloader,
we may get an error from the jump to program entry control request sent
to the device, which should be ignored.

TEST= plug in fx3 test device
fx shell usb-test-fwloader firmware.img
fx shell runtests -t usb-test

Change-Id: I2400197a1d3f76b4beea1cd574cfd175c8e31bd8

[zircon][usb-request] Move usb request struct to usb protocol header

usb-request.c is being moved out of the ddk folder and its fucntionality
is either moved into the usb protocol or the usb library. As part of
this effort, this changeset moves the usb_request_t and friends to usb
protocol header.

Test: Build. Tested usb mass storage on vim2

Change-Id: I31659e51d5f6e899d5eb747e7baa86602c0329ea

[zircon][ulib] Move usb out of driver ulib

This changeset moves usb.c out of the driver ulib and adds a separate
library for itself. In a later changeset some of the usb-request.c
functionality will move in into this library.

Test: Build. Sanity test of usb on vim2

Change-Id: I4807a3327943a71b5b88b22ab5c49756b042d969

[dev][fx3] Loads firmware onto FX3 for usb testing.

The usb-test-fwloader app reads the firmware image into a vmo,
and passes the vmo to fx3 to load and run.

TEST= plug in FX3 board, copy firmware image to zircon and run
fx shell usb-test-fwloader firmware.img

Change-Id: I472121179c92686574e888c85be026bc5eae081c