rowan: Add preMP keys to vbutil_what_keys
rowan: Add preMP keys to vbutil_what_keys

BUG=none
BRANCH=ToT
TEST=ensure Rowan PreMP keys are correctly output by
     'vbutil_what_keys chromeos_9547.0.0_rowan_recovery_canary-
channel_premp.bin'

Change-Id: I292425106a0b2d8e42f8a31de18edd0e63618842
Reviewed-on: https://chromium-review.googlesource.com/514984
Commit-Ready: Patrick Berny <1b893f69cc6232d24cedf099f60497e30e3b6bbb@chromium.org>
Tested-by: Patrick Berny <1b893f69cc6232d24cedf099f60497e30e3b6bbb@chromium.org>
Reviewed-by: Patrick Berny <1b893f69cc6232d24cedf099f60497e30e3b6bbb@chromium.org>
Reviewed-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>

coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot