Add per-platform flag run_preos, which indicates whether to run
preos ucode or not. Leave it to false for all known boards.
Bug 1799537
Bug 1815139
Change-Id: I1818970b0f70f636277443d6de199d3683fc565a
Signed-off-by: Terje Bergstrom <tbergstrom@nvidia.com>
Reviewed-on: http://git-master/r/1233410
(cherry picked from commit 8bea05dbfa64af88587edb8927a8ec71c6b0d807)
Reviewed-on: http://git-master/r/1239956
GVS: Gerrit_Virtual_Submit