vboot2: Replace hard coded 'fallback' prefix with Kconfig variable

Change-Id: I9cbdf06f4d0956b5374915f8af7501c6f75b4687
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: http://review.coreboot.org/10113
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
1 file changed