usb: dfu: introduce dfuMANIFEST state

usb: dfu: introduce dfuMANIFEST state

on nand flash using ubi, after the download of the new image into
the flash, the "rest" of the nand sectors get erased while flushing
the medium. With current u-boot version dfu-util may show:

Starting download: [##################################################] finished!
state(7) = dfuMANIFEST, status(0) = No error condition is present
unable to read DFU status

as get_status is not answered while erasing sectors, if erasing
needs some time.

So do the following changes to prevent this:

- introduce dfuManifest state
  According to dfu specification
  ( http://www.usb.org/developers/devclass_docs/usbdfu10.pdf ) section 7:
  "the device enters the dfuMANIFEST-SYNC state and awaits the solicitation
   of the status report by the host. Upon receipt of the anticipated
   DFU_GETSTATUS, the device enters the dfuMANIFEST state, where it
   completes its reprogramming operations."

- when stepping into dfuManifest state, sending a PollTimeout
  DFU_MANIFEST_POLL_TIMEOUT in ms, to the host, so the host
  (dfu-util) waits the PollTimeout before sending a get_status again.

Signed-off-by: Heiko Schocher <hs@denx.de>
Cc: Lukasz Majewski <l.majewski@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Pantelis Antoniou <panto@antoniou-consulting.com>