npcx: Enable PWM when starting to spin fans
npcx: Enable PWM when starting to spin fans

Currently, the EC disables PWM for the fan with PWM=0 but it doesn't
enable PWM when PWM goes up.

This patch ensures the corresponding PWM channel is enabled when the EC
starts spinnning a fan.

Signed-off-by: Daisuke Nojiri <fd5f93af191bf7e8f73ea71cc3c0f66b41b1dd49@chromium.org>

BUG=b:109951096
BRANCH=none
TEST=Verify the followings on Teemo:
1. Fan stops when RPM=0
2. Fan starts spinning when RPM goes up from 0
3. Fan stops when entering S3/S5
4. Fan starts spinning when leaving S3.

Change-Id: I49654df81953dc22eb1e6f34cb6534886fee6343
Reviewed-on: https://chromium-review.googlesource.com/1096547
Commit-Queue: Daisuke Nojiri <fd5f93af191bf7e8f73ea71cc3c0f66b41b1dd49@chromium.org>
Tested-by: Daisuke Nojiri <fd5f93af191bf7e8f73ea71cc3c0f66b41b1dd49@chromium.org>
Reviewed-by: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1128051
Commit-Ready: Daisuke Nojiri <fd5f93af191bf7e8f73ea71cc3c0f66b41b1dd49@chromium.org>
Reviewed-by: Aaron Durbin <af0622ab041e8b0f8e5819838dcc93898196e71f@chromium.org>

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