gsctool: allow to pass optional value for --rma
gsctool: allow to pass optional value for --rma

It would be much easier to use the --rma command line option if it
allowed to pass the authentication code in a separate invocation.

This patch changes the behavior of the --rma command line option and
improves the help message to match actual features of gsctool.

When passed without an extra parameter it requests the Cr50 to
generate the RMA authentication challenge, prints the challenge on the
console as before, and then exits instead of waiting for the user to
enter the authentication code.

When the extra parameter is given, it is considered the authentication
code received from the server, the code is passed to the Cr50 and the
response is reported to the user.

BRANCH=none
BUG=b:37952913
TEST=verified the expected behavior:

  localhost tmp # ./gsctool -r -t
  Challenge:
   CCYAQ 5ZUDP 9Q8NY S7TQR 7PVUR ETX7P T5YQK NGV9S
   7TY8Z QY7H5 5DEH3 5EEWY UBJPA WN7YX SE35G TPS76
  localhost tmp # ./gsctool -t -r EYE3E
  Processing response...
  rma unlock failed, code 1
  localhost tmp # echo $?
  3
  localhost tmp # ./gsctool -t -r EYE3EWQG
  Processing response...RMA unlock succeeded.
  localhost tmp # echo $?
  0
  localhost tmp #

Change-Id: I2c61ff3a3ef1718eb4f192321bebd8caba388aeb
Signed-off-by: Vadim Bendebury <5515d6d2d0829cbe0dd0dcf2094aaded06d58514@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/722115

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