board/ti/am6{2, 4}x-sk: add arm-trusted-firmware v2.7 hash

We are going to enable BR2_DOWNLOAD_FORCE_CHECK_HASHES by default
to enforce downloads to have at least one valid hash including
those that use a custom version.

Signed-off-by: Romain Naour <romain.naour@smile.fr>
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>
2 files changed