Tianocore currently reads/writes a lot of NVRAM variables that
don't actually need to be saved. Occasionally some, specifically
related to the graphical/serial consoles, can become corrupted,
leading to a bricked device. To avoid this, temporarily restrict
the reading/writing of variables to Bootorder related ones
(starting with 'Boot') until a better solution can be found.
Test: build/boot google/eve, inject "bad" NVRAM data, observe
device boots normally instead of hanging with no display detected.
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>