meta-yadro: share boot initiator mailbox support

Boot Initiator Mailbox should be available on all our hardware.
This commit moves all required files and recipes to the meta-yadro.

(From meta-yadro rev: 9ee3c28294c6a87912edbcf09b999b926634f836)

Change-Id: Idc52bfb50c8f122662279a593de0ee40703ddb51
Signed-off-by: Alexander Filippov <a.filippov@yadro.com>
Signed-off-by: Ivan Mikhaylov <i.mikhaylov@yadro.com>
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>