taniks: change ksi threshold to 250mV
taniks: change ksi threshold to 250mV

Change ksi_threshold_mv to 250 for fix issue about key lost when press
thress or more keys on the same KSI at the same time.

BUG=b:228222444
BRANCH=none
TEST=make buildall -j

Signed-off-by: arthur.lin <e4aaf0d52e9f6ff431b2faea740a66ecae52be49@lcfc.corp-partner.google.com>
Change-Id: I9404d507db929a08bfac7e7921815680389214bf
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3585274
Reviewed-by: Parth Malkan <c3d09dcbffc3a0a63125afed46f55e5cbf5bb3a9@google.com>
Reviewed-by: Daisuke Nojiri <fd5f93af191bf7e8f73ea71cc3c0f66b41b1dd49@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec