cr50: Allow spihash extension command over USB

Execution of this command requires physical presence on the DUT, this
is why it is save to allow it over USB.

BRANCH=cr50, cr50-mp
BUG=chromium:812880
TEST=using modified gsctool verified that the command goes through and
     physical presence indication is requested

Change-Id: I0aa371d8aaa5a480cc12d5d16edad8497142f4b4
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/927796
Reviewed-by: Mary Ruthven <mruthven@chromium.org>
1 file changed