Sona: Blink LED when battery is low
Sona: Blink LED when battery is low

This patch makes the battery LED on Sona blink in white when the state
of charge is below 10%.

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

BUG=b:74940319
BRANCH=none
TEST=Verify battery LED blinks when soc is below 10%.

Change-Id: Iee731a63787496ac15d97555564c8b02e1923256
Reviewed-on: https://chromium-review.googlesource.com/1020660
Commit-Ready: ChromeOS CL Exonerator Bot <fa429e5907f00867f797423aea74327bb02c91b6@appspot.gserviceaccount.com>
Tested-by: Daisuke Nojiri <fd5f93af191bf7e8f73ea71cc3c0f66b41b1dd49@chromium.org>
Reviewed-by: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>

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