FROMLIST: opp: Add API for getting voltage from supplies

Add API to get voltage for multiple supplies from opp table

(am from https://patchwork.kernel.org/patch/10730753/)
(also found at https://lkml.org/lkml/2018/12/4/114)

BUG=b:109911488
Test=build and boot to shell

Change-Id: I6e3f4320429b9267e58bc34cc147b9adc41c88ec
Signed-off-by: Nick Fan <Nick.Fan@mediatek.com>
Reviewed-on: https://chromium-review.googlesource.com/1377753
Commit-Ready: Nicolas Boichat <drinkcat@chromium.org>
Tested-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-by: Nicolas Boichat <drinkcat@chromium.org>
2 files changed