arcada: lower i2c bus speed to 400kHz

The sensors on the i2c line do not operate reliably
at 1Mhz i2c bus speed. Lower to 400kHz

BRANCH=75,76
BUG=b:136676970
TEST=verify that i2c bus speed when from ~1Mhz to ~400kHz after
this change with an oscilloscope.

Change-Id: Ie970f76fe7408de17f92bfc9f22a951b635fd278
Signed-off-by: Jett Rink <jettrink@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1691309
Commit-Queue: Jack Rosenthal <jrosenth@chromium.org>
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
(cherry picked from commit 48765c68fc17b84902afc0a3bd5926e5721e669f)
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1693124
1 file changed