iteflash: re-connect to Cr50 after triggering sync sequence
iteflash: re-connect to Cr50 after triggering sync sequence

ITE SYNC sequence generation now requires rebooting the H1, which
means that the USB connection to the CCD host would be shut down. This
patch adds closing and re-opening of the connection when itflash
requests sending the ITE SYNC sequence.

BRANCH=none
BUG=b:75976718
TEST=using dragonegg P1 hardware verified that the EC can be
     reprogrammed over CCD by running the following command:

  $ ./build/dragonegg/util/iteflash -c -e -w build/dragonegg/ec.bin
  ...
  Verify 524288 bytes at 0x00000000
  \ 99%
  Verify Done.
  $

  also verified that the EC is running the new image.

Change-Id: I2a485a741d5e90ecc8c5a91f4cf4f29cfee04b73
Signed-off-by: Vadim Bendebury <5515d6d2d0829cbe0dd0dcf2094aaded06d58514@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1305116
Reviewed-by: Matthew Blecker <d18f4466f2802f9c78c5c14a42b8c21fdbfabfcd@chromium.org>

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