Add PSU callback to nyan platforms

This change adds PSU callback to nyan platforms to return correct
psu types.
 - big: battery
 - blaze: battery
 - kitty: AC_only

BUG=chrome-os-partner:33067
BRANCH=none
TEST=tested on big, blaze and kitty. got the correct psu type by
"mosys psu type".

Change-Id: I057a08b7517fa2c00fd2886fe5eb9453b5962c9e
Reviewed-on: https://chromium-review.googlesource.com/224872
Tested-by: Ken Chang <kenc@nvidia.com>
Tested-by: Titan Lee <titanlee@nvidia.com>
Reviewed-by: Shawn Nematbakhsh <shawnn@chromium.org>
Reviewed-by: David Hendricks <dhendrix@chromium.org>
Commit-Queue: Ken Chang <kenc@nvidia.com>
4 files changed