drm_hwcomposer: Add commit message validation to CI

Check the subject prefix starts with "drm_hwcomposer: " and we have
Signed-off-by tags for both author and committer.

Change-Id: Ib26b8e5cbeae2156014f2bbfb8703545bdc1decb
Signed-off-by: Sean Paul <seanpaul@chromium.org>
1 job for master in 33 seconds (queued for 1 second)
Status Job ID Name Coverage
  Style
passed #22354
checkstyle

00:00:33