Adjust the linter to skip `common` directories, as a board_info.txt
serves no purpose there.
This also changes `sort | uniq` to `sort -u` for efficiency.
Change-Id: I29639d8b620bcd4f2f7032802f375d79ac391535
Signed-off-by: Sean Rhodes <sean@starlabs.systems>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/89050
Reviewed-by: Martin L Roth <gaumless@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
