kunimitsu: Correct ADC calculation for VBUS.

According to MEC1322 datasheet, ADC VREF is 3V.

With the voltage divider on Kunimitsu, R1=180K and R2=20K,
so full ADC is equal to 30V if ADC VREF is 3V.

BUG=none
BRANCH=none
TEST=Checked value returned by adc console cmd.
20xxx mV is returned by Zinger.
14xxx mV is returned by Apple charger.

Change-Id: I155ce03e3c840740c1dc3a985a1d5cfcf3b40c30
Signed-off-by: Kevin K Wong <kevin.k.wong@intel.com>
Reviewed-on: https://chromium-review.googlesource.com/304192
Reviewed-by: Shawn N <shawnn@chromium.org>
1 file changed