Patch merged into coreboot/master: build system: strip quotes from CONFIG_CBFS_PREFIX in a single location

the following patch was just integrated into master:
commit 6dc85707193801ac7640919b160237058ca4d546
Author: Patrick Georgi 
Date:   Mon Nov 30 22:44:53 2015 +0100

build system: strip quotes from CONFIG_CBFS_PREFIX in a single location

Instead of having to remember to strip the quotes everywhere so that
    string comparisons (of which there are a few) match up, do it right at
    the beginning.

Fixes building the image with a .config where CONFIG_CBFS_PREFIX
    contains quotes.

Change-Id: I4d63341cd9f0bc5e313883ef7b5ca6486190c124
    Signed-off-by: Patrick Georgi 
    Reviewed-on: https://review.coreboot.org/12578
    Tested-by: build bot (Jenkins)
    Tested-by: Raptor Engineering Automated Test Stand 
    Reviewed-by: Martin Roth 
    Reviewed-by: Timothy Pearson

See https://review.coreboot.org/12578 for details.

-gerrit