usb_updater: close connection when no data is transferred
usb_updater: close connection when no data is transferred

When usb_updater is invoked with the '-f' option and without
specifying the binary file to transmit, the cr50 still enters the data
transfer mode, even though the host is not transferring anything.

As a result cr50 stays in the 'rx_outside_block' state until timeout
expires. Another usb_updater invocation fails if attempted before
timeout expiration.

The UPGRADE_DONE PDU sent by the host causes the state machine to
switch to the idle state immediately.

BRANCH=none
BUG=none
TEST=ran the following commands:
   usb_updater -f && usb_updater -f

  the second invocation used to fail before this change, now it succeeds.

Change-Id: Iceafeb30de6011975fbf47dabc7c6c494177c0f7
Signed-off-by: Vadim Bendebury <5515d6d2d0829cbe0dd0dcf2094aaded06d58514@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/415554
Reviewed-by: Bill Richardson <129945214b1d548d8e49b6c29c43094f8c78057f@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec