kevin: change pwm frequency to reduce EE noise
kevin: change pwm frequency to reduce EE noise

Currently we have EEnoise(Decap Switching Noise) from LCD PWM
Kevin use LCD Backlight Driver IC and PWM Frequency from EC
Current 10kHz frequency can make switching Noise easily.

BUG=chrome-os-partner:55169
BRANCH=None
TEST=measuring noise reduced, verifying there was no influence
to LCD/digitizer/tsp

Change-Id: I1e65e56a19177dadba0110de5678669288a8555a
Signed-off-by: Wonjoon Lee <b961a80bc33bbc19346c547d1234eeb868c7ae74@samsung.com>
Reviewed-on: https://chromium-review.googlesource.com/360003
Reviewed-by: Shawn N <5259333ce42e3ace6a73988cec7115ed9d3a661a@chromium.org>

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