Add "speed_config" for each I2C port configuration to set speed to
400KHz.
BRANCH=master
BUG=none
TEST=compiled/verified
Change-Id: Icb48733b87cefc92577547b1eab661a8cbb12be6
Signed-off-by: Chris Wang <chriswang@ami.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/22589
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>