Patch merged into coreboot/master: tpm2: handle failures more gracefully

the following patch was just integrated into master:
commit 731ef9b7ad7087918a37db2d1d79ee53dfa9091b
Author: Vadim Bendebury 
Date:   Thu Dec 15 21:49:23 2016 -0800

tpm2: handle failures more gracefully

When trying to bring up a device with a malfunctioning TPM2 chip, the
    driver currently gets stuck waiting for SPI flow control, causing
    bricked devices.

This patch puts a 100 ms cap on the waiting time - this should be
    enough even for a longest NVRAM save operation which could be under
    way on the TPM device.

BRANCH=gru
    BUG=chrome-os-partner:59807
    TEST=with a matching change in depthcharge, now a gru with corrupted
         SPI TPM comes up to the recovery screen (it was not showing signs
         of life before this change).

Change-Id: I63ef5dde8dddd9afeae91e396c157a1a37d47c80
    Signed-off-by: Vadim Bendebury 
    Reviewed-on: https://review.coreboot.org/17898
    Reviewed-by: Aaron Durbin 
    Tested-by: build bot (Jenkins)

See https://review.coreboot.org/17898 for details.

-gerrit