UPSTREAM: mainboard/lippert/frontrunner-af: Use tabs for indents

BUG=None
BRANCH=None
TEST=None

Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/16685
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

Change-Id: Id8b60d32d5bdaaa6c693dcf5db992ed975cc2400
Reviewed-on: https://chromium-review.googlesource.com/388882
Commit-Ready: Furquan Shaikh <furquan@chromium.org>
Tested-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>