Correct frequency + duty cycle register calculations according to
datasheet.
BUG=chrome-os-partner:32089
TEST=Manual on Samus. Set 50% duty cycle and probe on scope, verify that
duty cycle is actually 50% and frequency is exactly 100 Hz.
BRANCH=samus.
Change-Id: I1e2c0bb7e53110367c38987b369fbef44af90a7d
Signed-off-by: Shawn Nematbakhsh <shawnn@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/221790
Reviewed-by: Alec Berg <alecaberg@chromium.org>