Start migration to rocko with external repos

Start migration to rocko with external repos

This change bumps the external repos to the respective rocko branches.

Especially:
- consolidate on meta-freescale from git.yoctoproject.org
- try master of meta-security-isafw
  (repo is stale, no rocko branch - might have to disable)
- meta-boundary currently disabled (no rocko branch)

Otherwise we update to the latest rocko branch revision.
For poky we stick to rocko v2.4.1.

Bug-AGL: SPEC-1181

Change-Id: Ie9d9791795edd3fb2e73fb2bbcbec80e505780da
Signed-off-by: Jan-Simon Möller <jsmoeller@linuxfoundation.org>