samus: remove learn mode workaround for new boards
samus: remove learn mode workaround for new boards

Remove learn mode workaround for backboosting on all new board
revisions, starting with board 1.

BUG=chrome-os-partner:34938
BRANCH=samus
TEST=load on board with board revision 1 and make sure local var
use_bkboost_workaround is 0.

Change-Id: Ieccd7f86baca72d231b5e1491db824e53472eff7
Signed-off-by: Alec Berg <1a4429eeda29095a12e19a73405f80f5b7f37a63@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/241121
Reviewed-by: Duncan Laurie <70662b43bc1a20b57ded72a2b08be88dd0da4841@chromium.org>
(cherry picked from commit 7627bd21d0b6ed8a176439ab0240b9fb75a903bf)
Reviewed-on: https://chromium-review.googlesource.com/241454

thehobn/ec,thehobn/ec,thehobn/ec,thehobn/ec