Patch merged into coreboot/master: google/rambi: add explicit pull-down for ram-id

the following patch was just integrated into master:
commit 474a7c51cecfd2e37b315da9cfb25607f3ad84f1
Author: Matt DeVillier 
Date:   Tue Feb 7 22:07:56 2017 -0600

google/rambi: add explicit pull-down for ram-id

Some variants need the internal pull resistor on GPIO_SSUS_40
    set explicitly to pull down rather than disabling the pull,
    in order for the ram-id to be read correctly via GPIO.

Correct this by adding a function to enable and set the internal pull
    and define its use as needed in the board's variant.h.

Chromium source:
    branch: firmware-gnawty-5216.239.B
    /src/soc/intel/baytrail/baytrail/gpio.h#418
    /src/mainboard/google/gnawty/romstage.c#60

Test: boot 4GB Candy board and observe correct RAM id, amount detected

Change-Id: I8823c27385f4422184b5afa57f6048f7ff2a25ab
    Signed-off-by: Matt DeVillier 
    Reviewed-on: https://review.coreboot.org/18309
    Tested-by: build bot (Jenkins)
    Reviewed-by: Nico Huber 
    Reviewed-by: Paul Menzel

See https://review.coreboot.org/18309 for details.

-gerrit