samus: accel: fix initialization bug in tap gesture
samus: accel: fix initialization bug in tap gesture

Fix bug in tap gesture. When turning on tap detection, don't
clear the history circular array index. This was causing inconsitent
tap for battery recognition because the inner window sum of z-axis
data (sum_z_inner) was relying on subtracting out old historical
data and adding in the new data, but when the array index changed,
it was subtracting out the wrong old data. This really only came in
to play if there was significant z motion before the last wakeup.

BUG=none
BRANCH=samus
TEST=keep going to sleep and waking up and test that tap for
battery works every time.

Signed-off-by: Alec Berg <alecaberg@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/226591
Reviewed-by: Sheng-liang Song <ssl@chromium.org>
Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
(cherry picked from commit 13579c3570df0b7f3535d8c5499468761a482734)
Signed-off-by: Duncan Laurie <70662b43bc1a20b57ded72a2b08be88dd0da4841@chromium.org>

Change-Id: I55e00c805d504dd6d257a81f2cd25fe384a53257
Reviewed-on: https://chromium-review.googlesource.com/227142
Tested-by: Duncan Laurie <70662b43bc1a20b57ded72a2b08be88dd0da4841@chromium.org>
Commit-Queue: Duncan Laurie <70662b43bc1a20b57ded72a2b08be88dd0da4841@chromium.org>
Reviewed-by: Duncan Laurie <70662b43bc1a20b57ded72a2b08be88dd0da4841@chromium.org>

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