ARM: dts: Add sbs-battery dts fragment used by chromebooks

This patch creates a sbs-battery fragment for batteries connected
to the i2c tunnel of the cros-ec embedded controller.

Signed-off-by: Chris Zhong <zyw@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Douglas Anderson <dianders@chromium.org>