[emac] Remove unused drivers from the board Change-Id: If9ef4319701c3ea3c7102ded737aecac0289226d Reviewed-on: https://fuchsia-review.googlesource.com/c/boards/emac/+/1124832 Commit-Queue: Auto-Submit <auto-submit@fuchsia-infra.iam.gserviceaccount.com> Reviewed-by: Jerry Belton <jcecil@google.com> Fuchsia-Auto-Submit: Jiaming Li <lijiaming@google.com>