broadwell: Add configuration for tuning VR for C-state operations

Add some configuration options that allow tuning the VR for C-state
settings that may be able to reduce noise.

- Add option to enable slow VR ramp rate for C-state exit
- Add variable to configure the minimum C6/C7 voltage

BUG=chrome-os-partner:34771
BRANCH=broadwell
TEST=build and boot on samus

Change-Id: I01445d62fbfcf200b787b924d8d72685819a4715
Signed-off-by: Stefan Reinauer <reinauer@chromium.org>
Original-Commit-Id: ed8f355e60292c82791817ae31bff58ac2390a72
Original-Change-Id: I8af75b69c8b55d3e210170ee96f8e22c2fd76374
Original-Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/241950
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/9497
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
2 files changed