firmware: add verification response enum
firmware: add verification response enum

Add verification response enum per the design spec.

Change-Id: I7ecb388312798210ec768c134a4454dfceb7866b
Signed-off-by: Patrick Venture <36c53fa43f47f3fd67cb2fc38031827244d18a1f@google.com>

openbmc/phosphor-ipmi-flash