Add nvstorage / crossystem support for new vboot2 fields

This allows testing vboot2.  These fields are ignored by original
vboot firmware.

BUG=chromium:370082
BRANCH=none
TEST=manual
	crossystem -> fw_tried=A, fw_result=unknown, fw_try_next=A

	crossystem fw_tried=B
	echo $? -> 1
	crossystem -> fw_tried=A, fw_result=unknown, fw_try_next=A

	crossystem fw_try_next=B
	crossystem -> fw_tried=A, fw_result=unknown, fw_try_next=B
	crossystem fw_try_next=beats_me
	echo $? -> 1
	crossystem -> fw_tried=A, fw_result=unknown, fw_try_next=B
	crossystem fw_try_next=A
	crossystem -> fw_tried=A, fw_result=unknown, fw_try_next=A

	crossystem fw_result=trying
	crossystem -> fw_tried=A, fw_result=trying, fw_try_next=A
	crossystem fw_result=bupkis
	echo $? -> 1
	crossystem -> fw_tried=A, fw_result=trying, fw_try_next=A
	crossystem fw_result=success
	crossystem -> fw_tried=A, fw_result=success, fw_try_next=A
	crossystem fw_result=failure
	crossystem -> fw_tried=A, fw_result=failure, fw_try_next=A
	crossystem fw_result=unknown
	crossystem -> fw_tried=A, fw_result=unknown, fw_try_next=A

	crossystem -> fw_try_count = 0, fwb_tries = 0
	crossystem fw_try_count=6
	crossystem -> fw_try_count = 6, fwb_tries = 6
	crossystem fwb_tries=0
	crossystem -> fw_try_count = 0, fwb_tries = 0

Change-Id: I1532f3384f8c05de2a7ff3f35abcc35d18049491
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/205475
6 files changed