Electro: Add battery hint message
Electro: Add battery hint message

Showing which battery is useful when debug.

BUG=None
BRANCH=master
TEST=power on EC can see prompt

Change-Id: Ic83d667ae377dc787a776116e41b09f21ee5a3be
Signed-off-by: Ryan Zhang <50a92783d595cae957ab2a2aa8dfe1aa1d9433fd@quantatw.com>
Reviewed-on: https://chromium-review.googlesource.com/425212
Commit-Ready: Ryan Zhang <e4a8705cef436f57390dc61a62fd42bb85ceca03@gmail.com>
Tested-by: Ryan Zhang <e4a8705cef436f57390dc61a62fd42bb85ceca03@gmail.com>
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