Patch merged into coreboot/master: vboot/vbnv_flash: fix return value check for rdev_writeat()

the following patch was just integrated into master:
commit 1b5581c8d9a149bd28a74615bb416c7c7341d570
Author: Aaron Durbin 
Date:   Tue Aug 23 13:22:17 2016 -0500

vboot/vbnv_flash: fix return value check for rdev_writeat()

The return value check was incorect and checking for failure
    in the success path. Fix the return value check so that it
    actually checks for success.

BUG=chrome-os-partner:56151

Change-Id: Ie7960b89a916dec261015c97c3e0552be56b5b5d
    Signed-off-by: Aaron Durbin 
    Reviewed-on: https://review.coreboot.org/16303
    Tested-by: build bot (Jenkins)
    Reviewed-by: Furquan Shaikh 
    Reviewed-by: Paul Menzel

See https://review.coreboot.org/16303 for details.

-gerrit